i LIBRARY QF CONGRESS. 

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I LNUUifi^STATES OF AMERICA. 



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Chemistry of the Farm, 



R. WARINGTON, F.C.S, 








NEW YORK: 

ORANGE JUDD COMPANY, 

751 BKOADWAY. 

1882. 



Entered, according to Act of Congress, in the year 1882, by the 

ORANGE JXJDD COMPANY, 

In the Office of the Librarian of Congress, at Washington. 



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PUBLISHERS' PEEFACE. 



This work is offered in tlie belief that it will meet the 
wants of many intelligent farmers, and others interested 
in the cultivation of the soil, who, while they have 
neither the time nor the inclination to take up Chemistry 
as a study, would gladly learn the present relations of 
Chemistry to Agriculture. The author of this book 
occupies an important position at Rothamsted. The 
most casual reader of Agricultural journals is aware that 
this is the name of an old English estate to which the 
labors of Messrs. Lawes and Gilbert have given a world- 
wide reputation as a station where abundant means, ad- 
ded to the highest scientific ability, have been devoted to 
the elucidation of Agricultural problems, solely for the 
benefit of Agriculture. These labors are not for English 
agriculture especially, but have a world-wide applica- 
tion. The results which are freely given to the world, 
are those of experiments conducted in the field and 
stables, as well as in the laboratory, on a scale which 
gives them a practical value and commends them at once 
to the farmer as well as to the scientist. 

While the author modestly refrains from even a sug- 
gestion to that effect, we regard his work as in accordance 
III 



IV publishers' preface. 

with the latest results attained at the center of Agricul- 
tiiial investigation. 

The visitor at Eothamsted is struck with the thor- 
oughly practical character of everything about the place 
and the entire absence of anything like show. 

We were, during a visit last year, eppecially interested 
with the exhibition of the constituents of a piece of 
English pasture, in which the different grasses and other 
plants, including weeds, were given, not only in figures, 
but in parcels containing the plants themselves in their 
proper proportions. The author, in his Preface, ex- 
presses the hope that his work may be used for the 
teaching of Agriculture in schools. In this we must 
disagree with him. If any work will answer for the use 
of public schools, no doubt this one will take the first 
rank. 

The great obstacle to the use of this, or any similar 
work in schools, is the difficulty of finding teachers. 
Unless a teacher quite understands and is thoroughly 
imbued with his subject, he can not profitably instruct 
others. 

The author, in referring to the literature of the sub- 
ject, mentions such works as will be found useful to the 
student. Among these are Prof. Johnson's " How Crops 
Grow" and "How Crops Feed." These volumes are 
standard works of reference, abroad as well as at home. 
In place of the European works upon plant life and plant 
growth which the author recommends to English readers, 
we may mention Gray's * ' First Lessons " as superior to 
any other work in the language as an elementary work in 
the study of plant life. No farmer, be he American or 



publisher's preface. V 

otherwise, can read this volume without receiving very 
much valuable information and suggestions which will 
prove of real practical value. 

The language of the work is remarkably clear and con- 
cise, and avoids, so far as the subject will allow, the use 
of scientific technicalities. 

As in England the term cor7i is used, especially for 
wheat, and generally for the small grains, while in this 
country it especially applies to Indian corn or maize, it 
has been thought advisable in an American Edition to 
change the word to accord with general usage. Where 
Indian corn is referred to in the work it is mentioned as 
maize, the name by which it is generally known in Eng- 
land. 

The American reader should bear in mind the fact 
that the common or Field Bean of England is very differ- 
ent from the bean cultivated in this country. Garden 
forms of it, known as Windsor Bean, etc., are rarely tried 
by English gardeners in this country, but our hot sum- 
mers make it very uncertain, and it is not known here as 
a field crop. 

March, 1882. 



CONTENTS 



Chapter I. 
Plant Growth 9 

Chapter II. 
Sources of Plant Food 20 

Chapter III. 
Manures - - --- 29 

Chapter IV. 
Crops 41 

Chapter V. 
notation of Crops -- 53 

Chapter VI. 
Animal Nutrition • 62 

Chapter VII. 
Foods '72 

Chapter VIII. 
Relation of Food to Animal Requirements. 94 

Chapter IX. 
Relation of Food to Manure 107 

Chapter X. 
The Dairy - - 113 



VII 



THE CHEMISTRY OF THE FARM. 



CHAPTEK I 
PLANT GROWTH. 



The Comtituents of PZa^i^s.— Water— The combustible elements of vege- 
table matter — The proportion of ash constituents in various parts of 
plants — The essential and non-essential elements of the ash — Com- 
position of a crop of grass. Function of the Xe.t'es.— Assimilation of 
carbon from the air — Formation of vegetable substance — Plant res- 
piration—The transpiration of water. Function of the Roots.— Absorp- 
tion of ash constituents and nitrogenous matter from the soil— The 
excretion of useless matter by the plant— The part played by ash 
constituents. (?m/ima^ion.— General character of seeds— The con- 
ditions and processes of their germination. Pi,ant Development.— 
Annual plants— the order in which plant constituents are assimilated 
—Biennial and perennial plants— the storing up of food for a second 
season — spring sap rich in sugar. 

The first step towards a knowledge of plant chemistry 
must be an acquaintance with the materials of which 
plants are built up. 

The Constituents of Plants.— The most abundant in- 
gredient of a living plant is water. Many succulent 
vegetables, as turnips and lettuce, contain more than 90 
per cent, of water. Timber felled in the driest time 
seldom contains less, than 40 per cent, of water. 

If a branch of a tree is burned the greater part is con- 
sumed and passes away in the form of gas, but there is 
left behind a small quantity of white ash. The same 
happens if any other part of a plant is burned. The con- 
stituents which form the dry matter of plants maybe thus 
9 



10 THE CHEMISTRY OF THE FARM. 

conveniently divided into two classes — the combustible 
and tlie incombustible. 

The combustible part of plants is made up of five 
chemical elements — carbon, oxygen, hydrogen, nitrogen, 
and sulphur ; without these no i^lant is ever produced. 
Carbon generally forms about one-half of the dry com- 
bustible matter of plants. Nitrogen seldom exceeds 4 per 
cent, of the dry matter, and is generally present in much 
smaller amount. Sulphur is still smaller in quantity. 
The remainder is oxygen and hydrogen. 

The carbon, hydrogen, and oxygen form the cellulose, 
lignose, pectin, starch, sugar, fat, and vegetable acids 
which plants contain. The same elements united with 
nitrogen form the amides and alkaloids; and further 
united w^ith sulphur the still more important albumi- 
noids, which are essential constituents of all plants. 

The incombustible or ash constituents form generally 
but a small part of the plant. The timber of freely- 
growing trees sontains but 0.2 — 0.4 of ash constituents 
m 100 of dry matter. In seeds free from husk the ash 
is generally 2 — 5 per cent. In the straw of cereals 4—7 
per cent. In farm roots ^/^ — 8 per cent. In hay 5 — 9 
per cent. It is in leaves, and especially did leaves, that 
the greatest proportion of ash is found ; in the leaves of 
root crops the ash will amount to 10 — 25 per cent, of the 
dry matter. 

The incombustible ash always contains five chemical 
elements — potassium, magnesium, calcium, iron, and 
phosphorus, besides sulphur already mentioned. Iron is 
present in only very small quantity. These five elements, 
though forming a very small portion of the plant, are 
indispensable to its life. Besides the elements just 
named, an ash will generally contain sodium, silicon, and 
chlorine, with frequently manganese, and perhaps minute 
quantities of other elements. The supplementary ele- 
ments just named are not apparently essential to plant 



PLAINT GROWTH. 11 

life, though some of them discharge useful functions in 
the plant. 

The metals above-named occur in the plant as salts, 
being combined with phosphoric, nitric, sulphuric, and 
various vegetable acids, of which oxalic, malic, tartaric 
and citric acid are the most common. The metals are 
also sometimes present as chlorides. Phosphorus occurs 
in the form of phosphates ; silicon is present as silica. 
Sulphur occurs partly as sulphates, and partly as a 
constituent of albuminoids. In the ash of plants the 
nitrates, and the salts of the vegetable acids are found m 
the form of carbonates. 

It is common to speak of the combustible ingredients 
of a plant as ^^ organic," and the incombustible ingre- 
dients as "inorganic." This distinction is scarcely accu- 
rate, as those ash constituents which are indispensable 
parts of plants have, during the plant's life, as much 
right to be called '^ organic " as albumin or cellulose. 

In the following table will be found the average com- 
position of a crop of meadow grass weighing five tons 
when cut, and producing one and one-half ton of hay ; 
this will illustrate wJiat has just been said as to the con- 
stituents of plants. Further information as to the com- 
position of crops will be found on page 42. 

COMPOSITION OF A CROP OF MEADOW GRASS. 

Water 8,378 lbs. 

Carbon 1,3151 



Hydrogen 144 

Nitrogen 49 

Oxygen and Sulphur 1,105 

Pota^sh 56.3 

Soda 11.9 

Lime 28.1 

Magnesia 10 . 1 

Oxide of Iron 9 i ^ 

Pliospboric Acid 12.7 f^ 

Sulpliuric Acid 10.8 

Chlorine 16.2 

Silica 57.5 

Sand, etc 4.5 



- Combustible matter 2,613 Ibg. 



Ash 209 lbs. 



Total crop 11,200 



12 THE CHEMISTRY OF THE FARM. 

Plants obtain the elements of which they are built up 
partly from the soil, and partly from the atmosphere. 
From the soil they obtain, by means of their roots, all 
their ash constituents, all their sulphur, and nearly the 
whole of their nitrogen and water. From the atmosphere 
they obtain, through the instrumentality of their leaves, 
the whole, or nearly the whole of their carbon, with prob- 
ably small quantities of nitrogen and water. 

Function of the Leaves.— The source of vegetable 
carbon is the carbonic acid gas present in the atmosphere. 
Carbonic acid gas passes more readily through the cuticle 
of a plant than do the nitrogen and oxygen which make 
up the bulk of the atmosphere. The carbonic acid thus 
absorbed is decomposed within the chlorophyl cells of 
the plant under the influence of light, oxygen being 
evolved, and the carbon retained by the plant. All green 
parts of a plant probably share in this action, but it is 
preeminently the function of the leaves. The decompo- 
sition of carbonic acid does not proceed in darkness, or 
at a very low temperature. The rays of light most active 
in effecting the decomposition are the yellow and orange 
rays ; the blue, violet, and dark red rays of the spectrum 
have scarcely any influence. 

The oxygen gas given off by a green plant exposed to 
light is equal in volume to the carbonic acid decomposed, 
so that apparently the whole of the oxygen contained in 
the carbonic acid is returned to the atmosphere ; the re- 
action is, however, really more complicated, as water is 
probably decomposed at the same time as the carbonic 
acid. 

The exact nature of the reaction which takes place 
when carbonic acid is decomposed in the chlorophyl cells 
is still unknown. Starch, composed of carbon and the 
elements of water (C,,H,„0,), is undoubtedly among the 
earliest products. Starch being an insoluble substance is 



plajn't growth. 13 

converted into sugar (glucose) for the nourishment of 
distant parts of the plant, to which it is conveyed by the 
movement of the saj). In parts where growth is taking 
place, and new cells are being formed, the sugar of the 
sap is converted into cellulose, the substance which forms 
the cell walls, and of which the whole structure of the 
plant primarily consists. The conversion of starch into 
sugar and cellulose presents no chemical difficulties, as 
all these substances are carbo-hydrates, that is they are 
composed of carbon and the elements of water. 

The formation of albuminoids in the plant is not at 
present understood ; we can only say that they are con- 
stituted out of the carbo-hydrates and some of the simple 
n'trogenous substances, most probably amides, present in 
the sap. 

The vegetable acids in a plant are probably formed by 
oxidation ; most likely by the oxidation of some of the 
carbo-hydrates. 

' The fatty matter of a plant may be formed from carbo- 
hydrates ; or possibly from the splitting up of albumi- 
noids. 

We have just referred to oxidation as taking place in 
the plant. This is always going on in the interior during 
life, and as a result the plant is continually consuming a 
small quantity of oxygen, and giving out a small quantity 
of carbonic acid, an operation precisely similar to animal 
respiration. This action is not readily perceived during 
the day-time, being hidden by the opposite action of the 
chlorophyl cells, which absorb carbonic acid and evolve 
oxygen. If a plant is placed in darkness the respiratory 
action becomes manifest. The oxidation of matters 
already formed is an iniportant means for the production 
of new bodies. 

The decomposition of carbonic acid by green plants 
during daylight is of the utmost importance in maintain- 
ing an atmosphere suitable for the respiration of animals. 



14 THE CHEMISTEY OF THE FARM. 

An animal in breatliing inspires atmospheric air ; it 
expires air in which a part of the oxygen has been re- 
placed by carbonic acid ; the result of animal life is thus 
to accumulate carbonic acid in the atmosphere. Such 
accumulation would be injurious to health, but is pre- 
vented by the growth of plants. It has been calculated 
that an acre of forest, producing annually 5,755 lbs. of dry 
matter, will consume the carbonic acid produced by the 
respiration of 15.4 men. 

Besides carbonic acid, plants are apparently capable of 
absorbing a small quantity of ammonia through their 
leaves. The uncombined nitrogen of the atmosphere is 
not appropriated by plants. When rain occurs after severe 
drouth water may be taken up to some extent through 
the leaf. 

Plants which have no chlorophyl cells, and possess, 
consequently, no green color, do not decompose carbonic 
acid. We have familiar examples of such plants in the 
broomrape and dodder of our clover fields, and in the 
common fungi. The broomrape and dodder are fed by 
the juices of the plant on which they live as parasites. 
The fungi derive their carbon from the decayed vegetable 
matter in the soil. 

Another important function of leaves consists in the 
transpiration of water. This transpiration takes place 
through small openings in the under side of the leaves, 
known as stomata, which have the property of closing in 
dry air and opening in moist. Transpiration takes phice 
only in hght ; it will occur abundantly, even in an atmos- 
phere saturated with water, if the plant be only exposed 
to sunshine. A small amount of general evaporation, 
distinct from transpiration proper, may occur in dark- 
ness. The amount of water evaporated from the surface 
of a growing plant is very large ; land that has borne a 
crop is always much drier than a bare fallow. 

The results of transpiration to the plant are most im- 



PLA]SrT GROWTH. 15 

portant, the evaporation of water from the leaves being a 
principal cause of the rise of the sap, and the consequent 
drawing up of 'Water from the soil containing plant food 
in solution. 

Function of the Roots. —The roots of a plant are the 
organs by which it absorbs water from the soil, and with 
this water a variety of food elements are introduced. 

The roots take up apparently all the diffusible sub- 
stances (those capable of passing through a membrane) 
which are present in the water which they draw from the 
soil. The plant may thus receive a number of substances 
not actually required for its nutrition. 

The feeding power of roots is not, however, confined to 
the taking up of ready-formed solutions, they are also 
capable of attacking some of the solid ingredients of the 
soil, which they render soluble and then appropriate. This 
important action of roots exists in different degrees with 
different plants. The action only takes place at the points 
of contact between the rootlets and the particles of the 
soil, and is brought about by the acid sap which the roots 
contain. This action of roots probably plays an important 
part in the supply of phosphoric acid and potash to the 
plant, as these substances, especially the former of them, 
exist in the soil in difficultly soluble forms, and are rarely 
found in solution in the water present in soils. 

Besides furnishing the plant with its ash constituents, 
the root has the important function of supplying nitrogen; 
this is nearly always taken up in the form of nitrates. A 
plant is capable of making use of nitrogen in the form of 
nitric acid or ammonia ; it also, according to several ex- 
perimenters, is able to assimilate nitrogen when in the 
form of urea, uric and hippuric acids, and several other 
amide bodies. The facility, however, with which ammonia 
and other nitrogenous substances, are converted into nitric 
acid in the soil is so great that nitrates become by far the 



16 THE CHEMISTRY OF THE FARM. 

most important source of nitrogen at a plant's disposal. 
Most plants are unable to assimilate the nitrogenous 
humus contained m soil. 

The very weak solutions taken up by the roots are 
concentrated in the upper parts of the plant, the water 
being rapidly evaporated by the leaves, as already men- 
tioned. The essential ash constituents are employed in 
the formation of new tissues. The non-essential ash 
constitaents which have been taken up by the roots are 
partly disposed of in a solid form, as a permanent incrus- 
tation of the older tissues. The soluble salts which are 
not thus disposed of, at first accumulate in the sap, and 
are probably more or less removed from the surface of the 
leaves and stem by the washing e^ect of rain. 

The deposition of silica upon the external tissues of 
wheat, barley, and other graminaceous plants is a familiar 
example of the excretion of a non-essential ash con- 
stituent. Silica is also abundant in the old leaves, and 
in the outer bark of many trees, and is commonly found 
as an incrusting constituent of old tissues. Insoluble 
calcium salts, frequently the oxalate, are also deposited 
as incrusting matters in old tissues. These incrustations 
are indirectly of service to the plant, as they tend to 
harden the tissues and thus protect them from injury. 

Soluble non-essential ash constituents, as chloride of 
sodium, are found abundantly in the succulent parts of 
plants when such ash constituents have been present in 
the soil. They generally diminish in quantity as the 
plant matures, and are never stored up in the seed. 

The amount and composition of the ash of succulent 
plants, as meadow grass, clover, and mangel, is greatly 
influenced by the character of the soil, and the manure 
applied. The ash of a seed, on the other hand, is very 
constant in composition, resulting from the selective 
powers of the plant. 

Of the particular action of the ash constituents within 



PLANT GROWTH. 1";* 

the plant little is known. Phosphoric acid and potash are 
undoubtedly the most important of the ash constituents ; 
they are always found concentrated in those parts of the 
plant where cell growth is most active, as, for instance, 
in the layer (cambium) between the wood and bark of a 
tree, and are abundantly stored up in the seed. 

Silica was long supposed to be an essential constituent 
of wheat, barley, and other similar plants, and to be the 
ingredient on which the stiffness of their straw chiefly 
depended. It has been shown, however, that maize may 
be successfully grown without any supply of silica, and 
with no perceptible difference as to the stiffness of the 
stem. The grass growing on peat bogs contains scarcely 
any silica, though silica is abundant in ordinary hay. 

Germination. — The seed is a storehouse of concentrated 
plant food, intended to nourish the germ until the root 
an^leaf are developed. In the seeds of the cereals, and of 
many other plants, the chief ingredient is starch. 
Another class of seeds, of which linseed and mustard- 
seed are examples, contain no starch, but in its place a 
large quantity of fat. A seed generally contains a con- 
siderable amount of albuminoids ; its ash is rich in phos- 
phoric acid and potash. 

For germination to take place, moisture, oxygen, and 
a suitable temperature are necessary. Under these con- 
ditions the seed swells, oxygen is absorbed, a part of the 
carbonaceous ingredients is oxidized, heat is developed, 
and carbonic acid evolved. During these changes the 
solid ingredients of the seed gradually become soluble ; 
the starch and fat are converted into sugar ; the albu- 
minoids are converted into amides — as for instance aspara- 
gine, probably also into peptones. With this supply of 
soluble food the radicle and plumule are nourished ; they 
rapidly increase in size, emerge through the coats of the 
seed, and, if the external conditions are suitable, soon 



13 THE CHEMISTRY OF THE FARM. 

commence their separate functions as root and leaf. The 
process of germination may be easily studied in the 
ordinary operation of malting barley. 

Seeds buried too deeply in the soil may not germinate 
for lack of oxygen. Or if germination takes place the 
plumule may fail to reach the surface, the store of food in 
the seed being exhausted before the layer of soil is pene- 
trated, and daylight reached. The smaller the seed, the 
less, as a rule, should be the depth of earth with which 
it is covered. 

Plant Development, — The development of the plant 
after germination follows a regular course. With au 
annual, which produces seed and dies during the first 
season, we have first a great development of root and 
leaf, which collect and prepare materials for growth ; 
next comes the formation of a flower stem ; and lastly, 
the production of flower and seed ; after which the plant 
dies. 

The materials furnished by the root preponderate in the 
young plant ; but as the plant matures, the proportion 
of carbon compounds derived from the action of the 
leaves steadily increases. A cereal crop contains at the 
time of full bloom all the nitrogen and potash which 
is found in the mature crop , the assimilation of phos- 
phoric acid continues somewhat later ; the increase of 
carbon and silica proceeds as long as the plant is in a 
green state. 

When seed formation begins an exhaustion of the other 
parts of the plant sets in, starch, albuminoids, phosjDhoric 
acid and potash being transferred from the root, leaf, and 
stem, and stored up in the seed. If the season is a good 
one, and the development of the seed fully accomj^lished, 
the straw of the crop is left very thoroughly exhausted ; 
while in a bad season it will retain far more of the mate- 
rials acquired during growth. For the same reason straw 



PLANT GROWTH. 19 

cut while the crop is still green is far more nutritlTe than 
when perfect ripeness has been attained. 

With a biennial or perennial crop the case is somewhat 
different. The first development of root and leaf is the 
same as in an annual ; but towards the end of summer 
there is a storing up of concentrated plant food in the root 
or stem to serve for the commencement of growth in the 
following spring. In a biennial root crop, the turnip for 
instance, the root attains a great size in autumn, the leaves 
dying after transferring to the root their most important 
constituents. The next season the root throws up a 
flower stem, and the store of matter accumulated during 
the preceding autumn is consumed in the production of 
seed. With the production of seed the root is exhausted 
and the plant dies. 

In trees plant food is stored up at the end of summer 
in the pith, the pith rays, and in the layer between the 
wood and bark. The leaves which fall in autumn have 
lost nearly all their starch, albuminoids, phosphoric acid 
and potash, these having been transferred to the stem. 
By the action of the sun in spring-time the new buds 
swell, the sap rises, the starch and other matters deposited 
in the wood during the previous autumn are re-dissolved, 
and employed at once for the production of new growths. 
The sugar found in maple sap during spring results from 
the transformation of starch stored up in the preceding 
autumn. 



CHAPTER II. 
THE SOURCES OF PLANT FOOD. 

The Atmosphere. — The carbonic acid, ammonia, and nitric acid which it 
supplies — The quantity of combined nitrogen and chlorides contained 
in rain. The soil. — Its origin — Properties of sand, clay, calcareous 
matter, and humus ; their relation to water and heat — The plant food 
contained in soil, its quantity, and condition — Losses by drainage — 
The absorptive power of soils — Influence of tillage, drainage, and 
burning. 

The Atmosphere. — We have already stated that the 
whole of the carbon of plants is obtained from the car- 
bonic acid present in the atmosphere ; 10,000 volumes of 
of air contain about Sy^ volumes of carbonic acid, or 
about 1 lb. of carbon in 3,500 cubic yards of air. This 
small amount is made sufficient by the action of winds, 
which bring an enormous quantity of air in contact with 
both soil and plant. 

The atmosphere also contains a very small and variable 
quantity of ammonia. Schloesing found from 1 lb. in 
6,000,000 cubic yards, to 1 lb. in 119,000,000 cubic yards. 
The quantity is greatest, according to the same experi- 
menter, in warm southerly winds. The ammonia of the 
air is directly absorbed by plants to a very small extent, 
it is rendered available chiefly through absorption by the 
soil, and by means of rain, which brings it in solution to 
the earth. 

The atmosphere also furnishes a small amount of nitric 
acid. The nitrogen and oxygen of the atmosphere com- 
bine under the influence of electric discharges, nitrous 
acid being formed ; this is converted into nitric acid by 
the action of ozone, or peroxide of hydrogen. This 
formation of nitric acid in the atmosphere is the only 
original source of combined nitrogen, on our globe, the 
20 



THE SOURCES OF PLANT FOOD. 21 

existence of which has been placed beyond dispute. 
Nitric acid may also be formed in the atmosphere by the 
oxidation of ammonia by ozone and peroxide of hydrogen. 

The total amount of nitrogen, in the form of ammonia 
and nitric acid, annually carried to the soil by rain, varies 
in different years and places. The average of many ex- 
periments on the continent gives 10.23 lbs. of nitrogen 
per acre. The average of two years' experiments at 
Rothamsted gave 7.29 lbs. The continental average is 
probably rather above the truth for the open country, 
many of the determinations having been made near towns. 

Rain also furnishes small quantities of alkaline chlo- 
rides, especially in the neighborhood of the sea ; sulphates 
are also present. At Cirencester the chlorides in the rain 
are on an average equal to about 53 lbs. of common salt 
per acre per annum ; at Rothamsted in Hertfordshire the 
quantity is about 22 lbs. 

The Soil. — All soils have been produced by the dism- 
tagration of rocks, generally through the prolonged 
action of water, air, and frost. The character of a soil 
largely depends on the character of the rock from which 
it has been derived. Primitive and igneous rocks yield 
soils rich in potash ; fossiliferous rocks produce soils rich 
in phocphoric acid. The principal ingredients of soils 
are sand, clay, carbonate of calcium and humus ; as each 
of these preponderate the soil is said to be sandy, clayey, 
calcareous, or peaty. 

Sand is either composed of pure quartz (silica), or con- 
sists of fragments of more complex minerals — mica, for 
example. When the former is the case, the sand will 
supply no plant food ; but in the latter case the gradual 
decomposition of the mineral will slowly increase the ash 
constituents available for the plant. 

Clay is a silicate of aluminium, produced by the decom- 
position of felspar and other silicates ; if absolutely pure 



22 THE CHEMISTRY OF THE FARM. 

it would furnisli nothing to the plant ; it always, however,. 
contains some potash, and frequently a considerable quan- 
tity. Clay has the important property of absorbmg and 
retaining phosphoric acid, ammonia, potash, lime, and 
other substances necessary for plant nutrition. 

The calcareous matter of soils supplies lime to the 
plant ; limestone also generally contains phosphoric acid. 
Carbonate of calcium is beneficial to the soil in many 
ways. It preserves the particles of clay in a separate 
coagulated condition, thus making heavy soils friable and 
pervious to water. It enables clay to exercise its absorbent 
power on various salts, which would otherwise escape its 
action. It also jDromotes the decomposition of vegetable 
matter, and the formation of nitrates in the soil. The 
presence of some salifiable base is essential for the ^er- 
formance of the chemical operations belonging to a fertile 
soil ; the salifiable bases usually present are either 
carbonate of calcium, or the alkalies derived from the 
decomposition of silicates. 

The humus, or decayed vegetable matter of soils, has 
its origin in the dead roots, leaves, etc., of a previous 
vegetation. It is the principal nitrogeiious ingredient of 
soils. A black soil, rich in humus, is sure to be also 
rich in nitrogen ; a soil destitute of humus will contain 
scarcely any nitrogen. The fertility of virgin soils is 
largely due to the nitrogenous humus which they contain. 

Of all soil ingredients sand has the least, and humus 
the greatest capacity for retaining w^ater. Light sandy 
soils thus suffer most from drouth, while applications 
of farm-yard manure, or the plowing in of green crops, 
increase the water-holding power of the soil by increasing 
the proportion of humus. The capillary power of soil, 
by which water is raised from the subsoil to the surface 
m dry weather, is least in open sandy soils composed of 
coarse particles, and greatest in the case of loam or clay. 

Dark-colored soils absorb the greatest amount of heat 



THE SOURCES OF PLAKT FOOD. 23 

from the sun's rays, and liglit-colored soils least. The 
presence of humus is thus favorable to soil warmth. 
Quartz sand is an excellent conductor of heat ; chalk is a 
bad conductor. A soil rich in sand will thus be warmed 
or cooled more rapidly, and to a greater depth than a soil 
containing but little sand. Water has a very sonsiderable 
effect in cooling a soil, partly from its high specific heat, 
and partly from the immense consumjDtion of heat during 
its evaporation. A wet soil is always colder than a dry 
one. The drainage of wet land will thus result in a 
greater warmth of the surface soil, and consequently an 
earlier growth in spring. 

The 23roportion of plant food present in soils is very 
small, even when the soil is extremely fertile. The sur- 
face soil (first 9 inches) of a pasture may contain when 
dry 0.25 of nitrogen per cent., while soil of the same 
depth from a good arable field may yield 0.15 per cent., 
and a clay sub-soil 0.05 per cent. A good surface soil 
may contain 0.20 per cent, of phosphoric acid, or not un- 
frequently a smaller quantity. Potash varies much, 
rising to 1.0 ])ev cent, or more in some clay soils, but 
being generally much smaller. 

The weight of soil on an acre of land is, however, so 
enormous, that small proportions of plant food may 
amount to very considerable quantities. Nine inches' 
depth of arable soil (clay or loam) will weigh, when per- 
fectly dry, about 3,000,000 or 3,500,000 lbs. A pasture 
soil will be lighter, the first 9 inches weighing when dried 
and the roots removed about 2,250,000 lbs. Supposing, 
therefore, a dry soil to contain 0.10 percent, of nitrogen, 
phosphoric acid, or 'potash, the quantity in 9 inches of 
soil will be from 2,250 lbs. to 3,500 lbs. per acre. 

A large part of the elements of plant food contained in 
soils is present in such a condition that plants are unable 
to make use of it. A soil may contain many thousand 
pounds of phosphoric acid or of nitrogen, and yet be in 



24 THE CHEMISTRY OF THE FARM. 

a poor condition ; while a small dressing of readily avail- 
able food, as superphosphate or nitrate of sodium, may 
greatly increase the fertility. 

The nitrogen contained in humus is not in a condition 
to serve as a general plant food; cereal crops are appa-' 
rently unable to appropriate it ; leguminous crops, how- 
ever, possibly assimilate some humic matters. By the 
action of a minute Bacterium present in all soils, humus 
and ammonia are oxidized, and their nitrogen converted 
into nitric acid. Nitritication only takes place in moist 
soil, sufi&ciently porous to admit air. It is also necessary 
that some base should be present with which the nitric 
acid may combine : this condition is usually fulfilled by 
the presence of carbonate of calcium. Mtrification is most 
active at summer temperatures ; it ceases apparently near 
the freezing point. 

The fragments of rock present in soil, as stones, gravel, 
and sand, are as a rule of little value to a plant, the 
elements of plant food which they contain being in too 
insoluble a condition to be attacked by the roots. These 
fragments of rock may however be slowly decomposed by 
the mechanical action of frost, and by the chemical action 
of water, and their contents thus gradually made availa- 
ble to the plant. The solvent power of the water in a 
soil is greatly increased by the carbonic acid, and perhaps 
also by the humic acid it holds in solution. Water con- 
taining carbonate of calcium in solution is especially 
capable of attacking silicates. 

If water is allowed to drain through a soil it carries 
with it a part of the readily soluble matter which a soil 
contains. The substances chiefly removed by the water 
will be the nitrates, chlorides, and sulphates of calcium 
and sodium. When heavy rain falls these substances are 
washed into the subsoil, and partly escape by the nearest 
outfall into the springs, brooks, and rivers. The loss of 
nitrates from highly manured land during a wet season is 



THE SOURCES OF PLANT FOOD. 25 

very considerable. "When dry weather sets ii^ evaporation 
takes place at the surface of the soil, the water of the 
subsoil is slowly brought again to the surface by capillary 
attraction, and the salts it contains are concentrated once 
more in the upper soil, forming in some rare instances a 
white crust of salt upon the surface. Capillary attraction 
has little influence in the case of sandy soils. 

Of these readily soluble salts the nitrates are of the 
greatest importance to plant food. The quantity of 
nitrates in a surface soil will vary greatly, depending on 
the richness of the soil in nitrogen, the previous condi- 
tions as to temperature and moisture, the extent of recent 
washing by ram, and on whether the soil is or is not 
under crop. Where a crop is growing the nitrates will 
be kept nearer the surface, the evaporation of water from 
a growing crop being far greater than from a bare soil. 
The nitrates will also be constantly taken up by the roots, 
and employed as plant food. The loss of nitrates by 
drainage is thus far less when the land is under crop than 
in the case of a bare fallow. * 

Phosphoric acid, potash, and ammonia are very rarely 
found in drainage water. If a solution containmg phos- 
phoric acid, potash, or ammonia is poured on a sufficiently 
large quantity of fertile soil, the water which filters 
through will be found destitute of these substances. 
This retentive power of soil for phosphoric acid, potash, 
etc., is of the utmost importance in agriculture. The 
action is a complex one. All salts are doubtless retained 
to some extent by soil through mere mechanical adhesion ; 
salts, thus feebly retained, as nitrates and chlorides, can 
be easily removed by washing with water. Other sub- 
stances are, on the contrary, retained by chemical affin- 
ity ; these are not removed by washing, or but to a small 
extent. The ingredients of the soil which exercise a chem- 
ical retentive power are the hydrates of ferric oxide and 
alumina, the hydrous silicates of aluminium, and humus. 
2 



26 THE CHEMISTRY OF THE FAEM. 

Ferric oxide is a common ingredient of soils ; to it the 
red color of many soils is owing. To the presence of fer- 
ric oxide the retention of phosphoric acid is chieily due, 
an insoluble basic phosphate of iron being produced. 
Alumina acts in the same manner. Ferric oxide and 
alumina have also a retentive power for ammonia and 
potash, but the compounds formed are more or less de- 
composed by water. To the hydrous silicates the perma- 
nent retention of potash and other bases is probably 
chiefly due. Humus has a great absorbent power for 
ammonia. Other bases, as magnesia and lime, are also 
retained by soil, but in a less powerful manner than are 
potash and ammonia. 

Soils destitute of carbonate of calcium take up very 
little potash or ammonia when these are applied as salts 
of powerful acids, as for instance, the chlorides, nitrates, 
and sulphates. When carbonate of calcium is present 
the potassium or ammonium salt is decomposed, the base 
is retained by the soil, while the acid escapes into the 
drainage-water united with calcium. The addition of 
carbonate of calcium may thus greatly increase the reten- 
tive power of a soil for bases. 

The fertility of a soil is nearly connected with its 
power of retaining plant food. Sandy soils, from their 
small chemical retentive jDowei;, and free drainage, are of 
small natural fertility, and dependent on immediate sup- 
plies of manure. 

There can be little doubt that the plant food contained 
in soil which is capable of being taken up by roots, exists 
either in solution, or in the states of combination just 
referred to — that is in union with ferric oxide, hydrous 
silicates, and humus. Different crops have very differ- 
ent powers of attacking these various forms of plant food. 

The operations of tillage and drainage serve m se\'eral 
ways to increase the amount of plant food which is at 
the disposal of a crop. 



THE SOURCES OF PLANT FOOD. 27 

By tillage tlie surface soil is kept in an open porons 
condition, favorable for the distribution of roots. By 
this means also capillary attraction is diminished, and the 
land consequently suffers less from drouth ; the water- 
holding power of the surface soil is also increased. A 
more important result of tillage is that the soil is 
thoroughly exposed to the influence of the air. Soils 
containing humus or clay will absorb ammonia from the 
atmosphere, and thus increase their store of nitrogen. 
The organic remains of former crops and manuring are also 
oxidized, the nitrogen being converted into nitric acid. The 
rocky fragments which a solid contains, as fragments of 
silicates or limestone, will at the same time be more or less 
disintegrated by the combined action of water and air, 
assisted by the carbonic and humic acids arising from the 
oxidation of vegetable matter, and a portion of the insol- 
uble plant food be thus brought into a state suited for 
assimilation by the roots of crops. In winter time the 
disintegration of the various ingredients of the soil is 
greatly assisted by frost. Water in freezing expands, arUl 
thus rends asunder the substance frozen. Of the various 
results brought about by tillage, the increased production 
of nitrates mast be ranked among the most important. 

By drainage the various chemical actions we have just 
mentioned are carried down to a greater or less extent 
into the subsoil, for as the water level is lowered the air 
enters from above to fill the cavities in the soil. By 
drainage also the depth to which roots will penetrate is 
increased, for roots will not grow in the absence of oxy- 
gen, and rot as soon as they reach a permanent water 
level. In a water-logged soil deoxidation is active, the 
nitrates present are destroyed, a part of the nitrogen 
being envolved as gas ; the soil may thus suffer a consid- 
erable loss of plant food. 

Burning is occasionally resorted to as a means of in- 
creasing the available plant food, and improving the 



28 THE CHEMISTRY OF THE FARM. 

texture of a heavy soil. The soil is burned in heaps, which 
are then spread over the land. If the soil contains 
limestone it is easy to see that the phosphates of the lime- 
stone may become more available by the complete disin- 
tegration which attends the conversion into lime. The 
lime will also attack the silicates of the soil at a high 
temperature, and liberate a part of the potash from its 
insoluble combinations. To produce the best results it 
is essential that the burning should take place at a low 
temperature. This treatment by burning is a very ex- 
treme one, and can be recommended only in a few cases ; 
it must always be attended with an entire loss of the 
nitrogen in the soil burned. The plowing in of burned 
clay is of use in improving the texture of heavy land. 



CHAPTER III. 
MANURES. 

Difference between natural vegetation and agriculture — ^necessity for 
manuring. Farm-%jard J/a/iwre.— Cireumstances which influence its 
character ; its average composition ; slowness of its effect— Seaweed 
similar to farm-yard manure — Ghmno — Sulphate of Ammonium— Ni- 
trate of Sodium— Soot, Dried Blood, and Woollen Sef use— Bones- 
Ground Phosphates— Superphosphate— Gypsum — Lime, Chalk, and Marl 
— Ihtassium Salt.' — Common Salt— Application of Manure — Import- 
ance of thorough distribution— Best time for application— The re- 
turn made by the crop. 

In the natural vegetation of a forest or prairie the soil 
suffers no diminution of plant food. The elements taken 
from the soil are returned to it on the decay of the plants 
which the soil has nourished, or on the death of the 
animals which have fed on these plants. Under these 
circumstances the surface soil becomes rich in carbon and 
nitrogen, the quantity contributed by the atmosphere 
exceeding all losses. The surface soil also becomes rich 
in the ash constituents of plants, these being collected 
from the subsoil by the roots, and left at the surface on 
the decay of the plant. A virgin soil thus generally con- 
tains an abundance of plant food, and will produce large 
crops without manure. 

In human agriculture, on the other hand, both vege- 
table and animal produce are consumed off the land 
that has reared them. Provision must therefore be made, 
sooner or later, to return to the land a part at least of 
the plant food removed from it, if permanent fertility is 
to be maintained. Hence the necessity for manuring. 

The most complete return to the land would be ac- 
complished by manuring it with excrements of the men 
and animals consuming the crops. This is partially done 
29 



30 THE CHEMISTRY OF THE FARM. 

by the application of barn-yard manure ; but the congre- 
gation of men in cities, and the difficulty of employing 
sewage with profit, prevent this plan being thoroughly 
carried out. The farmer is thus generally obliged to pur- 
chase manures for the land in exchange for the crops and 
stock sold off it. 

On very poor soils it is necessary to make a very com- 
plete return of all the elements of plant food removed by 
the crops, but in most soils there is an abundance of some 
one or more of these elements, and a partial manuring 
will consequently suffice. With high farming the con- 
tributions to the soil may be in excess of the exports, and 
the land consequently increase in fertility. The nature 
of the exhaustion resulting from the growth of particular 
crops, and the economic application of manure to meet 
their special requirements, will be considered in Chapter 
IV. The losses which a farm sustains by the sale of 
animal products will be treated of in the section on *^ The 
Constituents of Animals." 

Farm-yard Manure consists of the liquid and solid ex- 
crements of the 'farm stock, plus the straw employed as 
litter. Its composition will vary according to the char- 
acter of the animals contributing to it, the quality of their 
food, and the nature and proportion of the litter. The 
composition of the manure will also depend a good deal 
upon the method in which it has been prepared. 

In the case of an adult animal, neither gaining nor 
losing weight — a working horse for instance — the excre- 
ments will contain the same quantity of nitrogen and ash 
constituents as was present in the food consumed. If 
however the animal is increasing in size, is producing 
young, or furnishing milk or wool, the nitrogen and ash 
constituents in the excrements will be less than those 
contained in the food, the difference appearing as animal 
increase. The manure from animals of this class will 



MANURES. 31 

therefore be poorer than that obtained from the former 
class, supposing the same food given to each. We must 
not expect valuable manure from a cow in full milk, or 
from a rapidly growing pig. 

The character of the food will affect the quality of the 
manure even more than the character of the animal. A 
diet of -maize and straw chaff can yield only a poor ma- 
nure, because these foods contain a very little nitrogen 
or phosphates. A diet including a liberal amount of oil- 
cake or beans will, on the other hand, yield a valuable 
manure, these foods being rich in nitrogen and ash con- 
stituents. A common mode of increasing the supply of 
manure on a farm is by the consumption of purchased 
food by the stock. This part of the subject will be more 
fully discussed in Chapter IX. 

The treatment of the manure is also most important. 
A large proportion of the nitrogen is voided in the form 
of urine, and generally the richer the diet the higher will 
this proportion be. If, therefore, the manure is washed 
by rain, and the washings are allowed to drain away, 
serious loss will occur. Hence the superiority of box ma- 
nure to that made in an open yard. 

It must also be recollected that the urea, which forms 
the chief nitrogenous ingredient of urine, is speedily 
changed by fermentation into corbonate of ammonium ; 
as this is a volatile substance, a loss of a part of the nitro- 
gen may easily occur, especially if an insufficient amount 
of litter is employed. 

Farm-yard manure rapidly undergoes fermentation. If 
placed in a heap the mass gets sensibly hot, and a large 
quantity of carbonic acid is given off. When the fer- 
mentation occurs in a place protected from rain, carbona- 
ceous matter is destroyed, but little loss of nitrogen takes 
place. Kotten manure, when well made, is more concen- 
trated than the fresh, having diminished in weight dur- 
ing fermentation, with but little loss of valuable con- 



32 THE CHEMISTRY OF THE FARM. 

stituents. Some of the constituents have also become 
more sohible. 

Farm-yard manure will contain from G5 to 80 per cent, 
of water. The nitrogen may be 0.40 to 0.65 per cent., or 
higher, if produced by highly fed animals. The ash con- 
stituents will be 2.5 to 3.0 per cent., exclusive of the 
sand and earth always present. Of these ash constituents 
0.4 to 0.7 will be potash ; and 0.2 to 0.4 phosphoric acid. 
One ton of farm-yard manure will thus supply 9 — 15 lbs. 
of nitrogen, a similar amount of potash, and 4 — 9 lbs. of 
phosphoric acid. 

Farm-yard manure is a '^general" manure ; that is it 
supplies all the essential elements of plant food. The 
immediate return from an application of farm-yard ma- 
nure is much less than from the same amount of plant 
food applied in artificial manures. The effect of farm- 
yard manure is spread over a considerable number of 
years, its nitrogen being chiefly present not as ammonia 
but in the form of carbonaceous compounds, which de- 
compose but slowly in the soil. 

Seaweed when fresh is, on the whole, similar in value 
to farm-yard manure. It becomes more valuable as it 
loses water. 

Guano. — This manure consists chiefly of the dried ex- 
crements of sea fowl. When guano has been deposited 
in the absence of rain it contains a large amount both of 
nitrogenous matter and phosphates. If exposed to rain 
the original nitrogenous matter is decomposed, and the 
nitrogen volatilized in the form of carbonate of ammo- 
nium ; the guano remaining is then almost purely jdIios- 
phatic. Ichaboe guano, for example, is a recent deiiosit, 
containing about 12 per cent, of nitrogen, and 12 per 
cent, of phosphoric acid ; while Mejillones guano is a 
phosphatic guano, containing 0. 9 per cent, of nitrogen, 
and 32.5 per cent, of phosphoric acid. From its great 



MAJEURES. 33 

yariation in composition guano should always be pur- 
chased on analysis. 

In a nitrogenous guano the nitrogen is chiefly present 
as uric acid, and as ammonium salts. The strong smell of 
a damp guano is due to carbonate of ammonium. Tlie 
phosphoric acid exists principally in the form of phos- 
phate of calcium, but in nitrogenous guanos a small part 
exists as phosphate of ammonium, a salt readily soluble 
in water. Guano which has not suffered by washing may 
contain 3 to 4 per cent, of potash. 

Nitrogenous guano is a highly concentrated manure, 
and may be employed with excellent effect for grain crops, 
potatoes, and roots. Phosphatic guanos may be employed 
for turnips, but such guanos are more usually converted 
into superphosphate before they are applied to the land. 

Sulphate of Ammonium.— This substance is prepared 
from the ammoniacal products of gas works ; in its crys- 
tallized form it is the most highly nitrogenous of all the 
manures at a farmer's disposal, containing about 20 per 
cent, of nitrogen. 

It should be ascertained in every case that the manure 
is free from sulphocyanate of ammonium, as this substance 
is very injurious to plants. If sulphocyanates are pres- 
ent a solution of the salt will become blood-red on the 
addition of ferric chloride. 

Sulphate of ammonium is a '' special " manure, valua- 
ble solely for its nitrogen. It is a powerful manure for 
grain crops, for which it is best employed in conjunction 
with superphosphate. 

Nitrate of Sodium.— An enorm6us deposit of the crude 
salt, containing much chloride of sodium* is found in 
Peru. The nitrate sent to this country has been puri- 
fied by crystallization ; it will contain about 15. 6 per cent. 
of nitrogen. The most usual impurity is common salt. 

This manure, like the preceding, is valuable solely for 



34 THE CHEMISTRY OF THE FARM. 

its nitrogen. It is an excellent manure for all crops re- 
quiring artificial supplies of nitrogen, especially grain 
crops and mangels. For grain crops it is best employed 
together with superphosphate. Nitrate of sodium should 
not be mixed with a damp superphosphate, else nitric 
acid may be lost. It is best to mix the two immediately 
before use ; or the superphosphate may be sown with the 
grain, and the nitrate applied afterwards as a top-dressing. 
Nitrate of sodium is especially suited for clay land. It 
is quicker in its action than any other nitrogenous ma- 
nure, and is therefore the best manure to employ when a 
late dressing has to be given. 

Soot, Dried Blood, and Woollen Refuse are all purely 
nitrogenous manures. Soot owes its value to the pres- 
ence of a small and variable quantity of ammoDium salts. 
Dried blood is an excellent manure, containing 10 to 13 
per cent, of nitrogen. Shoddy, and other forms of wool 
and hair are very variable in composition, owing to the ad- 
mixture of dirt, grease, and other foreign matter ; the ni- 
trogen they contain will range from about 5 to 10 per cent. 

The nitrogen of blood, wool, and hair, is not in a form 
suitable as plant food. Blood readily decomposes in the 
soil, yielding ammonia and nitric acid. Wool and hair 
decompose much more slowly, and their effect is spread 
over many years. 

Soot is generally employed as a top-dressing for spring 
grain. Dried blood is an excellent manure for wheat. 
Wool and hair are chiefly used for hops. 

Bones. — These are largely employed as manure ; the 
fat is usually first extracted by steaming. Commercial 
bones contain about 3.6 per cent, of nitrogen, and 23 
per cent, of phosphoric acid, existing as phosphate of 
calcium. Bones that have been boiled to extract the 
gelatine contain much less nitrogen, but a larger propor- 
tion of phosphates. 



MANURES. 35 

Bones decompose but slowly in tlie soil, especially on 
heavy land ; their effect is thus spread over several years. 
The finer the bones have been ground the more imme- 
diate IS their effect. Bones are usually employed for pas- 
ture, and for turnips. 

Ground Phosphates. — Some phosphates when finely 
ground may on certain soils be successfully employed as 
manure without previous conversion into superphosphate. 
The phosphates most suitable for this purpose are phos- 
phatic guanos, bone-ash, and South Carolina phosphate. 
The soils most suitable for such manures are those rich 
in humus, and poor in carbonate of calcium ; these being 
the conditions (presence of humic and free carbonic acid) 
most favorable to the solution of phosphate of calcium. 
Pasture soils are especially suitable for such treatment. 
The solution of the ground phosphate may be facilitated 
by forming it into a compost with farm-yard manure be- 
fore its application, or by employing with it sulphate of 
ammonium. The phosphate should be employed in very 
fine powder. ' 

Superphosphate. — An abundance of mineral phosphates 
(phosphates of calcium) occur in nature ; many of these 
are so little soluble that their effect as manure is but 
small ; by treating them with sulphuric acid the sparingly 
soluble tricalcic phosphate is converted into the readily 
soluble monocalcic phosphate, sulphate of calcium being 
at the same time produced. Superphosj)hate is thus a 
mixture of monocalcic phosphate, and generally some 
free jDhosphoric acid, with gypsum, and various impuri- 
ties (as sand and compounds of iron and aluminium), 
derived from the original mineral. A superphosphate 
will always contain more or less of undissolved phos- 
phate ; this amount will be more considerable if the ma- 
nure is badly made, or if the original mineral contained 
much ferric oxide or alumina. 



36 THE CHEMISTRY OF THE FAEM. 

The yalue of a superphosphate chiefly depends on the 
percentage of " soluble phosphate " present. By this 
term analysts do not mean monocalcic phosphate, but the 
quantity of tricalcic phosphate rendered soluble. 

In England there is an excellent deposit m the Cam- 
bridge coprolite. This is largely used for making super- 
phosphate. Other coprolites are also employed, but they 
are less suitable. Immense quantities of mineral phos- 
phates are imported principally from South Carolina, 
Spain, Bordeaux, and Canada, besides considerable quan- 
tities of phosphatic guano. 

The superphosphates richest in soluble phosphate (40 
to 45 per cent.) are prepared from phosphatic guauos. 
Bone, ash, and some phosphorites, also yield high quality 
manures. The great bulk of our superphosphates is at 
present prepared from Carolina phosphate or coprolite ; 
such manure will contain 23 to 27 per cent, of soluble 
phosphate. 

Superphosphates form the basis of almost all manu- 
factured manures. By using bones, or by adding shoddy 
or crude ammonium salts, turnip manures are produced 
containing a small amount of nitrogen. By mixing with 
the superphosphate a larger amount of ammonium salts, 
or nitrate of sodium, the articles sold as gram, grass, 
mangel, and potato manures are prepared. Superphos- 
phate made largely from bones is known as dissolved 
bones. 

When superphosphate is applied to a soil containing 
carbonate of calcium, the soluble phosphate is speedily 
precipitated, but in a form easily taken up by the roots 
of plants. In most cases the phosphoric acid is finally 
conyerted into basic phosphate of iron, a substance at- 
tacked with difficulty by plants. 

Superphosphates are naturally more speedy in their 
effect than manures consisting of undissolved phosphate. 
A small quantity of phosphoric acid applied as super- 



MANURES. 37 

phosphate will have as great an effect as a considerable 
quantity applied as bones or ground phosphate. 

Superphosphate is chiefly employed for turnips^ for 
which it IS invaluable ; it is also of considerable use for 
grain crops, especially barley. Its use tends to early ma- 
turity m the crop. 

Gypsum.— This manure is one of limited value. It is 
composed of calcium and sulphuric acid, and is most 
suitable for crops, such as clover and turnips, which re- 
quire a considerable amount of sulphur. As superphos- 
phate always contains much gypsum, special applications 
of gypsum will be unnecessary where superphosphate is 
employed. 

Lime, Chalk, and Marl, are frequently manures of the 
greatest importance. On soils naturally destitute of lime, 
as is the case with many clays and sandstones, these ma- 
nures will supply an indispensable element of plant food. 
Some marls will also supply a notable quantity of phos- 
phoric acid. In most cases, however, the beneficial influ- 
ence of these manures is due to the chemical actions which 
lime performs m the soil ; the chief of these have been 
already glanced at under the head of '^ Soil." 

Burned lime is much more powerful in its action on vege- 
table matter than chalk or marl ; it should be used with 
discrimination, lest the humus of the soil be unduly di- 
minished. Heavy clays, or soils rich in humus, are those 
most benefited by burned lime. In reclaiming peat bogs 
lime is of the highest value. The acid humic matter of 
the peat is neutralized by the hme, and the nitrogen held 
m combination is converted into ammonia and nitric 
acid, and thus made available to a crop. 

The general effect of lime is to render available the 
plant food already m the soil, without itself supplying 
any significant amount ; limmg cannot, therefore, be suc- 
cessfully repeated except at considerable intervals. 



38 THE CHEAIISTKY OF THE FARM. 

Potassium Salts. — These salts are now obtained from 
Stassf urt and Leopoldshall in large quantities ; they form 
a thick deposit overlying an enormous mass of rock salt. 
The commonest potassium salt employed as manure is 
kainit ; it consists of chloride of potassium, sulphate of 
magnesium, and water, with frequently chloride of mag- 
nesium and common salt in addition. Kainit will contain 
13 to 14 per cent, of potash. Calcined kainit contains 
less water, and some magnesia in place of the chloride of 
magnesium ; it will contain 15 to 17 percent, of potash. 

Wood ashes may also be employed as a potash manure ; 
they will contain between 5 and 15 per cent, of potash. 
The ash of young boughs is richer than that from full- 
sized timber. 

Potash manures produce their greatest effect on pas- 
ture ; clover and turnips may also be benefited by their 
use. Many soils are naturally well furnished with pot- 
ash, on these soils potash manures are almost without 
effect. 

fomDioii Salt* — Chloride of sodium supplies no essen- 
tial ingredient of plant food. The little value which 
salt possesses as a manure is probably due to its action 
in the soil, where it may help to set free more important 
constituents. 

Application of Manures. — A manure can be efficacious 
only v^hen its constituents are brought into contact with 
the roots of the crop. To obtain this contact to the full- ' 
est extent the manure must be thoroughly and evenly 
distributed throughout the depth of soil mainly occupied 
by the roots. Soluble manures — as nitrate of sodium, 
chloride of sodium, ammonium salts, potassium salts, and 
superphosphate — have the great advantage that they dis- 
tribute themselves within the soil after the first heavy 
shower far more perfectly than can be done by any mode 
of sowing. When manure is especially required by the 



MAi;rURES. 39 

plant in its earliest stages — as superphosphate for turnips 
— it may be drilled with the seed ; but, as a rule, manure 
should be sown broadcast, and plowed in or harrowed. 

Top-dressing, that is sowing manure on the surface of 
land already under crop, should generally be confined to 
manures that are soluble, or the principal constituents of 
which easily become soluble in the soil. Nitrate of sodium 
is sown with advantage in this manner if showery weather 
can be depended on to distribute the manure in the soil. 
On pasture all manures are necessarily applied as top- 
dressings. 

Whenever possible, manure should be reduced to a fine 
powder before application. Artificial manures, if distri- 
buted by hand, should first be made up to a considerable 
bulk by mixing with fine dry soil or ashes. Manures con- 
taining ammonia must not be mixed with alkaline ashes, 
else some of the ammonia will be lost. 

Manures of little solubility, or those of which the soil 
has a great retentive power, may be applied to the land 
some time before the growing period of the crop. Dif- 
fusible manures, on the other hand, should be applied 
only when the crop is ready to make use of them, else 
serious loss may occur from drainage. Farm-yard manure, 
rape cake, and bones, and to some extent superphosphate 
and potassium salts, belong to the former class ; while 
nitrates, and all manures containing ammonia, belong to 
the latter class. It was formerly supposed that the great 
retentive power of fertile soils for ammonia would eifectu- 
ally prevent any loss by drainage ; we now know that 
ammonia is speedily converted into nitrates after mixing 
with the soil, and that these nitrates are readily washed 
out by heavy rain. 

Following these principles, an autumn manuring for 
what may consist of farm-yard manure, blood, or shoddy, 
with or without superphosphate ; but dressings of guano, 
ammonium salts, or nitrate of sodium should be deferred 



40 THE CHEMISTRY OF THE FARM. 

until the spring. The question is, howeyer, clearly one 
of climate, and with a dry winter climate ammonium salts 
or guano may be applied with advantage in the autumn. 

On soils of open texture, and little retentive power, 
preference must often be given to manures of little solu- 
bility, in order to diminish the loss occasioned by heavy 
rain. Bulky organic manures, as farm-yard manure or 
seaweed, are in such cases very suitable. 

No dressing of manure is completely taken up by the 
crop to which it is applied, dressingij larger than the 
actual requirements of the crop must therefore be applied 
to obtain a given result. Soluble and active manures 
produce their principal effect at once, and are of little 
benefit to subsequent crops. Sparingly soluble manures, 
and those which must suffer decomposition in the soil 
before they are of service to the plant, as farm-yard 
manure and bones, will on the contrary continue to pro- 
duce an effect over many years. Farmers have a preju- 
dice in favor of the latter class of manures, but it is clear 
that the quickest return for capital invested is afforded 
by the former class. 

Nitrogen applied as ammonium salts or nitrates will 
give all its effect during the first year ; 45 to 50 percent, 
of the nitrogen apjolied in this form to wheat and barley 
is, according to Lawes and Gilbert, recovered on an aver- 
age in the increase. In the case of farm-yard manure, 
applied on the heavy land at Eothamsted to wheat and 
barley, only about 10 to 15 per cent, of the nitrogen was 
recovered in the increase, but the effect on the barley 
continued many years after the application of the manure 
ceased. It is evident that a small quantity of an active 
manure will accomplish the same work as a large quantity 
of one less active. 

The residues of phosphatic and potassic manures are 
available for subsequent crops, but are distinctly less 
active than fresh applications of the same manures. 



CHAPTER IV. 
CROPS. 



The dry matter, nitrogen, and ash constituents, in average crops. Cereal 
(7y(^5. —Characteristic composition— Mode of feeding— Most suitable 
manuring. Meadow ifa?/.— Characteristic composition— Demand for 
ash constituents— Influence of manures on quantity and quality- 
Pasture especially suited for obtaining nitrogen from the atmosphere. 
Leguminous Crops.— Characteristic composition— Source of nitrogen 
obscure— Clover-sickness. Root Crops.— Characteristic composition 
—Differences in the nutrition of turnips, mangels, and potatoes. 
Fwest Growth— LsiVge production of dry matter for small consump- 
tion of ash constituents and nitrogen. Adaptation of Manures to 
Crops.— The feeding power of each crop must be taken into account- 
Economic distribution of manure in a rotation— The practical value 
of manures only known by experiments on each farm. Influence of 
Climate and Season. 

To understand the chemistry of crops we must first in- 
quire as to their composition. The following table gives 
the average composition of ordinary farm crops and of 
the annua! produce of three kinds of forest. The quan- 
tities of carbon, hydrogen, and oxygen present are omit- 
ted, also some of the smaller ash constituents. By " pure 
ash" is understood the ash minus sand, charcoal, and car- 
bonic acid. 

The composition of grain, and of all seeds, is tolerably 
constant ; but the composition of straw, leaves, roots, 
and tubers, will vary very considerably according to the 
character of the soil, manure, and season. 
41 



42 



THE CHEMISTRY OF THE FARM. 



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44 THE CHEMISTRY OF THE FARM. 

Cereal Crops, — These contain much less nitrogen than 
either the leguminous or root crops ; about three-quar- 
ters of the nitrogen is In the grain, and only one-quarter 
in the straw. The amount of phosphoric acid is not very 
different from that found in other crops ; this ingredient 
is, in fact, the most constant of all the constituents of 
crops ; it is chiefly concentrated m the grain. Potash 
and lime are present in much smaller quantity than in 
other crops ; they are chiefly concentrated in the straw. 

The presence of a large amount of silica is characteris- 
tic of the cereal crops ; they possess apparently a capacity 
for feeding on silicates not enjoyed by other crops. The 
base of the silicate is made use of by the plant, while the 
silica itself is excreted upon the surface of the leaves and 
straw. It has been shown that silica is by no means essen- 
tial for the growth of cereals ; they take it up freely, but 
can also do without it. 

The autumn sown cereals (wheat and rye) have both 
deeper roots, and a longer period of growth, than the 
spring sown cereals, "and are better able than the latter 
to supply themselves with the necessary ash constituents 
from the soil. Barley possesses a considerable develop- 
ment of root near the surface, and is apparently more 
capable of obtaining nitrogen from the soil than wheat. 

Cereal crops derive their nitrogen almost exclusively 
from nitrates ; the form in which the great bulk of the 
nitrogen is present in the soil is unsuitable for them. 
Notwithstanding, therefore, the small amount of nitrogen 
contained in cereal crops, they rank among those most 
benefited by nitrogenous manures. Phosphates, though 
of little use by themselves, are also beneficial (especially 
in the case of spring crops) when applied with nitroge- 
nous manure. A nitrogenous guano, or an application of 
nitrate of sodium and superphosphate, is generally the 
most effective manuring for a cereal crop. 



CROPS. 45 

Meadow Hay. — The grasses which form the main bulk 
of hay belong to the same family of plants as the cereal 
crops ; the seed, however, m grass bears such a small 
proportion to the stem and leaf that meadow hay may be 
regarded as a straw crop. In accordance with this 
character hay is found to contam a much larger propor- 
tion of potash and lime than cereal crops, and a much 
smaller amount of phosphoric acid. 

The roots of grass being far shorter than those of the 
cereals are less able to collect ash constituents from the 
soil ; if therefore grass is mown for hay, manures contam- 
ing potash, lime, and phosphoric acid will generally be 
required. Like the cereal crops grass is greatly increased 
in luxuriance by the application of soluble nitrogenous 
manures. 

Farm-yard manure, or the feeding of cake, grain, or 
roots on the land, is the most appropriate manuring for 
permanent pasture, if quality as well as quantity of pro- 
duce is considered. Large crops of hay may be obtained 
by manuring with nitrate of sodium, together with kamit 
and superphosphate, but a continuance of such treatment 
promotes a coarse herbage. 

The natural clovers of a meadow are destroyed by the 
continued application of highly nitrogenous manures, a 
hay consisting almost exclusively of grass being produced . 
The clovers are developed by the application of manures 
supplying potash and lime, and by pasturing instead of 
mowing. 

The perennial character of grass, and the abundance of 
humus in a pasture soil, present favorable conditions for 
the collection of nitrogen from the atmosphere ; this 
takes places to a greater extent on pasture land than with 
most other crops. 

Leguminous Crops. — Some of these are grain crops, as 
beans and peas ; others are fodder crops, as red clover, 



46 THE CHEMISTRY OF THE FARM. 

sainfoin and lucerne, A striking characteristic of all 
these crops is the large amount of nitrogen which they 
contain, the quantity being about twice as great as that 
found in cereal crops. The quantity of potash and lime 
in leguminous crops is also very large. The relative 
proportion of these two bases varies much in crops grown 
on different soils ; upon a calcareous soil lime will pre- 
ponderate in the crop, but on a clay soil potash. The 
lime IS found chiefly in the leaf. Silica is nearly absent 
in leguminous crops. 

The nutrition of leguminous crops is not at present 
perfectly understood. A good croj) of red clover, when 
cut for hay, removes a large quantity of nitrogen from 
the land, but it nevertheless leaves the surface soil actually 
richer m nitro2:en than it was before from the residue of 
roots and stubble left m the soil. From whence is this 
large quantity of nitrogen obtained ? It must be pro- 
cured either from the subsoil, or the atmosphere. The 
former seems the more probable, as experiments have 
hitherto failed to prove that leguminous plants have any 
special power of obtaining nitrogen from the air. The 
question is further complicated by the fact that nitroge- 
nous manures generally produce but little effect upon 
leguminous crops. It seems pretty certain that legumi- 
nous crops possess to some extent a distinct source of 
nitrogen ; they are probably capable of feeding on some 
compounds of nitrogen and carbon which are compara- 
tively useless to other crops, and hence the facility with 
which they acquire nitrogen from the soil. A deeply 
rooted crop like red clover collects nitrogenous comi30unds 
from the subsoil, and accumulates nitrogen at the surface 
in the form of a crop. 

The particular food supply of a leguminous crop 
becomes exhausted by repeated cropping, and the land is 
bean sick ; " no means of remedy- 



CROPS. 47 

ing this condition is known saye by the growth of other 
crops for a series of years. 

Potash manures have generally a very beneficial effect 
upon leguminous crops ; they fail, however, to cure clover 
sickness. Gypsum is also valuable, though to a less 
extent. 

Root Crops. — All these crops contain a large amount 
both of nitrogen and ash constituents ; among the latter 
potash greatly preponderates. Turnips contain more 
sulphur than any other farm crop. 

The turnip and mangel crop differ in several respects. 
Turnips and swedes draw their food chiefly from the 
surface soil. Their power of taking up nitrogen from 
the soil is distinctly greater than that of the cereal crops. 
Turnips are also well able to supply themselves with 
potash when growing in a fertile soil, but they have 
singularly little power of appropriating the combined 
phosphoric acid of the soil ; fresh applications of phos- 
phatic manures thus always produce a marked effect on 
this crop. 

Mangels have far deeper roots than turnips, and also a 
longer period of growth. They have a great capacity for 
drawing food from the soil, including both nitrogen, 
potash, and phosphoric acid. When carted off the land 
they are probably the most exhaustive crop that a farmer 
can grow. As mangels have not the same difficulty that 
turnips have of attacking the combined phosphoric acid 
of the soil, phosphatic manures are, in their case, of much 
less importance. Purely nitrogenous manures, as nitrate 
of sodium, when applied alone to mangels, generally pro- 
duce a great effect on the crop ; this is not the case with 
turnips, which require phosphates as well as nitrogen in 
their manure. 

As both turnips and mangels consume extremely large 
amounts of plant food, a liberal general manuring with 



4:3 THE CnEMIoTRY OF THE FARM. 

farm-yard manure is in most cases essential for the pro- 
duction of a full crop ; but the special characteristic of 
the manure for turnips should be i)hosphatic, and of that 
for mangels nitrogenous. 

Potatoes are surface feeders, and require a liberal gen- 
eral manuring to ensure an abundant crop. 

As both root crops and potatoes require large supplies 
of potash, kainit will be found of service on land naturally 
poor in that ingredient. It will be chiefly required when 
the crops are raised with artificial manures only, as farm- 
yard manure will always supply a considerable amount of 
potash. 

Forest Growth. — The figures given in the table repre- 
sent the composition of the produce of beech, spruce fir, 
and Scotch pine forests felled for timber, and are the 
results of extensive investigations made in Bavaria. 
Nitrogen, sulphur, and chlorine determinations are 
wanting. 

The amount of dry matter in the annual forest gro\^tli 
is in excess of that yielded by any of the cultivated crops 
given in the table, excepting mangels. This large produce 
is obtained by a very small consumption of soil food ; the 
amounts of potash and phosphoric acid required are 
especially far less than in the case of any farm crop. The 
greater part both of the ash constituents and nitrogen is 
found in the fallen leaves ; if these are left undisturbed, 
and allowed to manure the ground, the requirements of 
the forest become extremely small. It appears that about 
3,000 lbs. of perfectly dry pine timber are produced with a 
consumption of only 1^ / ^ lbs. of potash, and 1 lb. of phos- 
phoric acid per acre per annum ; with beech timber the 
quantities required are rather larger. The nitrogen con- 
tained in timber is very small in amount, but the actual 
quantity required by a forest has not been accurately 
ascertained. The growth of forest timber is plainly far 



CROPS. 49 

less exhaustive to the soil than ordinary farm culture. 
The demand on the soil becomes, however, considerably 
greater if the trees are cut when young, young timber and 
small branches being far richer both in nitrogen and ash 
constituents than the mature wood. 

Adaptation of Manure to Crops.— The true economy 
of manure can be understood only when we are acquainted 
with the special characters of the crops we cultivate. The 
composition of a crop is no sufficient guide to the character 
of the manure appropriate to it, even when we possess in 
addition the composition of the soil on which it is to be 
grown. It is not only the materials required to form a 
crop, but the power of the crop to assimilate these 
materials which must form the basis of our judgment. 
This fact has been much overlooked by many scientific 
writers, who have counselled farmers to manure their land 
in every case with all the constituents required by the 
crop, a proceeding both impracticable and unnecessary. 
In the case of a barren sand it may indeed be requisite to 
supply all the constituents of plant food before a crop can 
be grown, but such a case is far from the circumstances of 
ordinary agriculture. 

When land is in a fertile condition the total amount of 
plant food aA^ailable for crops is very considerable, and 
luxuriant growth may be obtained by supplementing the 
stores of the soil with the few particular elements of food 
which the crop it is Avished to grow has most difficulty in 
'obtaining. Thus, in a large majority of cases, a dressing 
of nitrate of sodium and superphosphate will ensure a full 
crop of wheat, barley, or oats, and in many cases nitrate 
of sodium alone will prove very effective. These cereal 
crops generally find the supply of nitrates in the soil 
insufficient for their full growth, and the supply of 
phosphates more or less inadequate ; but in a majority of 
cases they are well able to obtain a sufficient supuly of 
3 



50 THE CHEMISTRY OF THE FARM. 

potash, and other essential elements of food. We are 
thus able, by supplying one or two constituents of the 
crop, to obtain a luxuriant harvest. In the same way 
nitrate of sodium employed alone will, in most cases, 
produce a large crop of mangels ; superphosphate alone, a 
large crop of turnips ; while potassium salts alone may be 
strikingly effective with j^asture and clovers. 

This special manuring for each crop is no strain on the 
capabilities of the soil if a rotation of croj)s be followed. 
If superphosphate is applied for the turnips, potash for 
the seeds, and a nitrogenous manure for the cereal crops, 
the more important elements of plant food contained in 
the soil will not be diminished at the end of the rotation. 
At the same time the most economic result will have been 
obtained from the manures employed, for each manure 
will have been supplied to that particular crop with which 
it yields the most remunerative result. 

It is doubtless possible by means of rotations manured 
on the above principles to farm successfully with the sale 
of all the crops produced, and without the use of farm-yard 
manure ; this is possible at least so long as artificial 
manures can be obtained at a low price. In the majority 
of cases, however, the special manuring will only be 
required to supplement the general manuring by farm- 
yard manure. Under these circumstances it would seem 
best, from a chemical point of view, to apply the farm-yard 
manure to those crops which most require potash, or 
which stand most in need of a general manuring ; such 
crops would be pasture, seeds, turnips, and potatoes. 

The economic value of potash manures varies much on 
different soils. As potassium salts are an expensive 
manure, the farmer should always ascertain by means of 
small field experiments whether they will, in his case, 
yield a remunerative result, before employing them on 
any large scale. 

As the whole object of artificial manuring is to supple- 



CKOPS. 51 

ment the deficiencies of tlie soil, it is highly desirable 
that a farmer should ascertain by trials in the field what 
is the actual amount of increase which he obtains from 
the application of the manures he purchases. A few care- 
fully made experiments will teach him what his land and 
crops are really in need of. Should he add superphosphate 
with the nitrate of sodium for his wheat ? What dressing 
of the nitrate is most economical ? Is superphosphate alone 
sufficient for his turnip crop, or should guano or nitrate be 
employed as well ? What is the smallest quantity of 
superphosphate sufficient for the crop ? Will it pay to 
use potassium salts for his seeds or pasture ? These and 
many other questions can only be answered by trials on 
his own fields, and on the farmer's knowledge of such facts 
will depend the economy with which he is able to use 
purchased manures. 

luflucnce of Climate and Season. — The influence of 
weather upon crops is far greater than the influence of 
manure. 

As a plant contains water as its largest constituent, and 
as the whole of the plant food obtained from the soil is 
taken up through the medium of water, while the amount 
of water daily lost by the plant through evaporation is very 
large, the necessity of a sufficient supply of water in the 
S0il during the growing period of a crop is very evident. 
On the other hand, an excess of water in the soil prevents 
root development, and causes a loss of nitrates and other 
soluble plant foods in the drainage water. Deeply- rooted 
crops, as wheat, red clover, and mangel, are those best 
fitted to resist drouth ; while shallow-rooted crops, as 
grass and turnips, are those which suffer most from it. 

We have already seen that carbon, which forms the 
largest ingredient of all vegetable substances, is obtained 
by plants exclusively from the atmosphere under the in- 
fluence of light, and that a certam temperature is necessary 



52 TUE CnEMISTEY OF THE FAKM. 

for this assimilation of carbon, and for tlie other chemical 
processes which proceed in a growing plant ; a sufficient 
supply of light and heat is therefore plainly required for 
the production of a crop. In a season of deficient light 
and heat the harvest is always late, growth having taken 
place more slowly than in an average season. In the case 
of extremely cold and cloudy summers the whole season 
may be too short for maturing the crop, and the seed in 
consequence may never be fully ripened. 

Each crop requires more or less a different climate for 
its perfect development; a knowledge of the kind of 
climate best suited to each croji is of great service in 
selecting crops for any particular district. Thus wheat 
requires hot and dry weather for its ripening period, while 
oats will ripen in a moist atmosphere. Mangels require 
heat, and can resist drouth, while turnips develop best 
in a cool, moist air. 

The soil best furnished with plant food is the one which 
will yield the best results in adverse seasons, the crop 
having a greater amount of vitality, and being able to 
turn to the best advantage the short periods of favorable 
weather that may occur. Poor soils yield their best results 
in seasons of slow but continued growth, the crop having 
a longer time to collect the scanty supply of food which 
the soil contains. In hot seasons, with an early harvest, 
only soils well supplied with food can produce full crops. 

The character of the winter has often considerable in- 
fluence on that of the following season. In a wet winter 
the soil may lose nitrates by drainage to a considerable 
extent. Root development will also be prevented by ex- 
cessive wet. After such a winter the wheat crop gener- 
ally is in a backward condition, and finds itself in an 
impoverished soil. The injurious effects of severe frost 
are well known. 



55 



CHAPTER Y. 

ROTATION OF CROPS. 

The aim of rotations— Results of bare fallow— Effect of green crops, fed 
on the land or plowed in — Distinctive characteristics of crops — 
Differences in periods of growth, depth of roots, powers of assimi- 
lation, and quantity of food demanded — Losses to the land during 
rotation — Actual loss in an assumed four-course rotation — Probable 
gain of nitrogen from the atmosphere— Sale of produce other than 
corn and meat. 

It is by no means impossible to grow the same crop 
with success year after year on the same land ; ordinary 
pasture is indeed an example of continuous cropping. 
The Rothamsted experiments show that excellent crops of 
wheat, barley, and mangel may be continuously obtained 
if appropriate manure is annually applied, and the land 
kept free from weeds. A rotation of crops is resorted to 
in ordinary practice from the facilities which such a plan 
affords for cleaning the land, and from the greater econo- 
my of manure which results from this practice. One of 
the principal aims of a rotation is to bring the land from 
time to time mto a condition suitable for growing cereal 
crops ; this suitable condition consists mainly in the 
accumulation of nitrogenous plant food in the surface 
soil. 

Bare Fallow. — A bare fallow is one of the oldest modes 
of preparing soil for wheat. The soil is plowed, and 
exposed a whole year to atmospheric influences, and 
finally sown with wheat. In the case of a clay soil, this 
treatment would probably lead to the following results: — 

1. An improvement m the mechauical texture of the soil. 

2. The disintegration of some of the mineral silicates, 
whereby potash and other necessary ash constituents of 

53 



THE CHEMISTKT OF THE FAEM. 

plants would be liberated and made available for vegeta- 
tion. 3. The absorption of ammonia from the atmosphere 
by the soil. 4. The receipt of both ammonia and nitric 
acid from the air in the form of rain. 5. The oxidation 
of ammonia and of the vegetable remains in the soil, 
nitric acid being produced. 

The production of nitric acid is probably the most 
important result of a bare fallow. In soils at Rothamsted 
left as bare fallow, there has been found at the end of 
summer 34 — 55 lbs. of nitrogen per acre in the form of 
nitric acid in the first 20 inches from the surface. Sup- 
posing the season of fallow is a fairly dry one, the increase 
in the available nitrogenous food will probably enable the 
soil to produce twice as much wheat as it could do with- 
out this treatment. If, however, the soil is exposed to 
heavy rain, the nitrates produced will be more or less 
washed out, and the benefit of the fallow greatly dimin- 
ished. Bare fallow can be used systematically with ad- 
vantage only on clay soils having a considerable absorptive 
power for ammonia, and in a tolerably dry climate ; 
under other circumstances a continuance of the practice 
must issue in a serious loss of soil nitrogen. 

Green Crops. — The most usual plan for bringing land 
into condition for the growth of cereals is the cultivation 
of greon crops. These may be plowed in, forming what 
is termed green manuring ; or consumed on the land by 
the farm stock ; or the crop may be removed, consumed 
in cattle-sheds or in the farm-yard, and the resulting 
manure brought on to the land. The principle in every 
case IS that the constituents of the crop shall be returned 
to the soil. 

Let us suppose that land is laid down with seeds, which 
after two or three years are plowed up, and a cereal crop 
taken. While the land is continuously covered by vege- 
tation the loss of nitric acid by drainage will be reduced 



ROTATIOIT OF CROPS. 55 

to a minimum. If the grass is fed off on the land, the 
surface soil will at the end of the three years be consid- 
erably enriched both with ash constituents and nitrogen. 
The former have been collected from the subsoil by the roots 
of the crop, and returned to the surface as animal manure. 
The latter includes the accumulated receipts from the 
atmosphere during the three years, minus the quantity 
lost by drainage and that assimilated by the animals. 
The accumulated nitrogen will be chiefly in the form of 
grass roots, stems, and humus. When such land is 
plowed up, the vegetable matter and humus are oxidized, 
and gradually yield their nitrogen as nitric acid. 

Such a mode of cropping has an advantage over a bare 
fallow in several ways : — 1. The land is turned to profit- 
able use, food being produced for the farm stock. 2. Both 
ash constituents and nitrates are collected from the sub- 
soil, and brought to the surface. 3. The nitrogen is 
kept in an insoluble form, as vegetable matter, and con- 
sequently cannot be washed away, but accumulates to a 
greater extent than in a bare fallow. 4. Humus is pro- 
duced, the beneficial actions of which have already been 
noticed. We have laid no stress on the enrichment of 
the land by means of ammonia taken up from the atmos- 
phere by the leaves of the crop, for nothing is known as 
to the quantity of nitrogen which crops may thus acquire. 

It follows from what we have just stated that the ben- 
efits resulting from the growth of a green crop in a rota- 
tion are greater in proportion as its period of growth is 
longer, and its roots deeper. The more these conditions 
are fulfilled the larger will be the accumulation at the 
surface both of nitrogen and ash constituents, and the 
greater consequently the increased fertility of the soil. 

Leguminous crops, as already mentioned, have a special 
power of accumulatmg nitrogen in the surface soil, and 
are hence of the greatest value in a rotation. Eed clover 
is the most striking instance of this action. Its roots 



56 THE CHEMISTRY OF THE EAEM. 

extend further perhaps than those of any other farm crop, 
and being biennial it has a long period for growth. The 
accumulation of nitrogen at the surface in the form of 
roots, stubble, and decayed vegetable matter, is in the 
case of a good crop of clover so considerable, that the 
whole of the above ground growth may be removed as hay, 
and the land yet remain greatly enriched with nitrogen, 
and in an excellent condition for producing a croj^ of 
wheat. 

The plowing in of green crops has some advantages 
over the feeding of crops on the land. By this mode of 
proceeding the whole of the crop is returned to the soil, 
whereas in feeding a small part of the nitrogen and ash 
constituents is retained by the animal. The character- 
istic advantage of green manuring lies, however, in the 
large amount of humus which the soil acquires. All the 
carbon which the crop has obtained from the atmosphere 
is in this case incorporated with the soil, instead of being 
consumed by the animal. Green manuring is especially 
adapted for light sandy soils, which need humus to in- 
crease their retentive power. 

Having glanced at the general advantages to be de- 
rived from alternating green crops with cereals, we will 
consider next the characteristics of different crops which 
specially fit them to succeed or prepare for each other. 

Distinctive Characteristics of Crops.— Differences in 
their periods of growth occasion a marked distinction in 
the relation of different crops to soil nitrogen. Thus the 
fact that the active growth of the cereals commences m 
spring, and concludes at their time of blooming towards 
the end of June, places these crops at a disadvantage as 
to the supply of nitrates from the soil. The autumn 
and winter rains have frequently washed out the greater 
part of the nitrates contained in the soil before the 
growth of the cereal crop commences, and nitrification in 



ROTATIOI^ OF CROPS. 57 

the soil lias not long recommenced its activity in summer 
time wten the crop becomes too mature to appro^jriate 
fresh supplies of nitrogen. Continuous wheat cropping 
thus results in a gradual impoverishment of soil nitrogen 
by winter drainage, over and above the nitrogen actually 
removed m the crops, and thus necessitates a considera- 
ble application of nitrogenous manure if fertility is to be 
mamtained. 

A root crop sown in early summer, on the other hand, 
has at its disposal all the nitrates that would be available 
for wheat or barley, and in addition the large supply of 
nitrates formed in the soil during summer and early 
autumn. A great part of the nitrates which would be 
lost in cereal cultivation is thus assimilated and retained 
by a root crop, and such crops are found to stand in less 
need of nitrogenous manure than cereals. By consum- 
ing the roots on the land the nitrates collected by the 
crop are returned to the soil in the form of animal ma- 
nure, and the land thus prepared to carry a cereal crop. 
Similar remarks might be made respecting other green 
crops whose active growth extends into the autumn.* 

Another important difference between crops lies in 
their range of roots. Deeply-rooted crops, as red clover, 
sainfoin, rape, and mangel, and among the cereals wheat, 
and rye, are to a considerable extent subsoil feeders, and 
have a greater power of obtaining ash constituents from 
the soil than shallow-rooted crops, as white clover, pota- 
toes, turnips, and barley. In accordance with this we 
find that superphosphate is a very effective manure for 
the last three crops, but is much less required by such 
crops as mangel or wheat. By growing deeply-rooted 
crops as part of a rotation the subsoil is made to con- 
tribute to the general fertility. Shallow-rooted crops, on 



*The writer is indebted to Mr. Lawes for the important ideas con- 
tained in the two preceding paragraphs. 



58 THE CHEMISTET OF THE FARM. 

the other hand, have generally a special faculty for ap- 
propriating food accumulated at the surface, and are often 
of great use in this respect, as when barley is made to 
follow turnips fed off on the land. 

Very little is definitely known as to the capacity of 
different crops for assimilating different forms of plant 
food, but there can be no doubt that this also is one of 
the distinctions between various crops, and one reason of 
the economy of a rotation. The most plainly marked 
distinction as to mode of feeding is afforded by the be- 
havior of various crops towards silica. Graminaceous 
crops, as the cereals and grasses, are apparently capable 
of assimilating certain of the silicates contained in the 
soil ; other crops exhibit no such capacity. In such a 
case it is easy to imagine that an alternation of cereals 
with crops of a different description may be for the bene- 
fit of both, each drawing to some extent upon distinct 
supplies of food. Again, leguminous crops are clearly 
able to assimilate nitrogen to a far greater extent than 
cereals, and probably in some measure from a different 
source. If crops of winter beans and winter wheat are 
grown on similar unmanured land, the bean crop will 
generally contain twice as much nitrogen as the wheat. 
The land is not however impoverished for wheat by the< 
growth of beans, for wheat after beans will be a far better 
crop than wheat after wheat, thus affording a striking 
example of the advantages of rotation. 

The quantities of plant food required by different crops 
are given in the table printed on page 42 ; these also fur- 
nish reasons for the alternation of crops. It will be seen, 
for instance, that the cereals require but little potash and 
lime, while root crops, beans, and clover, demand a large 
supply ; it is obvious, therefore, that the resources of the 
soil are husbanded by growing these two classes of crops 
in alternation, the greater demand for potash and lime 
thus falling every alternate year. 



ROTATTO:^^ OF CEOPS. 



59 



The net result of a judicious alternation of crops, in 
which the special characteristics of each are turned to 
good account, is the production of a maximum total yield 
of produce with a minimum amount of manure. 

Losses to the Land during Rotation. — The table show- 
ing the composition of ordinary farm crops will supply 
the requisite information as to the loss which a farm may 
suffer by the sale of individual crops. We will now con- 
sider briefly the losses during a rotation. 

The conservation of plant food on a farm is generally 
effected by confining the exports to grain and meat, the 
rest of the produce being consumed by the stock, and the 
manure returned to the land. Let us assume that a farm 
is managed on the four-course system, and that the 
average crops obtained per acre are — swedes, 14 tons ; 
barley, 40 bushels ; seeds (half clover, half grass), 3 tons 
of hay ; and wheat, 30 bushels. Further, that nothing 
is sold save grain and meat ; that 2 bushels both of wheat 
and barley are returned to the land as seed ; that 700 lbs. 
of linseed cake are fed with each acre of swedes ; that 
110 lbs. of oats are purchased per acre per annum for the 
horses. Finally, that half a ton of straw is fed per acre 
in the course of the rotation, and the rest used as litter. 
The soil will in this case suffer the following losses of 
nitrogen, phosphoric acid, and potash, in the course of a 
four-years' rotation. 

LOSSES PER ACRE DURING A FOUR-COURSE ROTATION. 





Nitrogen. 


PJiosphoric 
Acid. 


Potash. 


By feeding Swedes, 14 tons 

By sale of Barley, 38 bushels 

By feeding Seeds, 3 tons hay 

By sale of Wheat, 28 bushels 

By feeding Straw, i ton 


lbs. 
11.1 
32.3 

18.7 

30.8 

0.7 


lbs. 

1.89 
14.35 

3.20 
13.35 

0.12 


lbs. 
0.24 
9.60 
0.40 
9.05 
0.02 


1 :3.6 . 

Deduct Manure from 440 lbs. Oats,' 
and 700 lbs. Oil-cake 36.8 


32.91 
14.61 


19.31 
12.02 


1 Total loss in 4 years 56.8 i 18.30 


7.29 


' Average loss each year 


14.2 


4.57 


1.82 



GO THE CHEMISTRY OP THE FAKM. 

These losses assume that the farm-yard manure is prop- 
erly made, and returned to the land without waste. If 
the manure has suffered loss by drainage the estimates 
given would have to be increased. 

The loss of potash is extremely small, and may gener- 
ally be quite disregarded. If, however, no cake is used, 
and the land is poor in potash, the loss might be replaced 
by the use of 1 cwt. of calcined kainit for the seeds. 

The loss of phosphoric acid would be more than re- 
placed, even if no cake were employed, by the use of 2 
cwt. of superphosphate for the swedes. 

The loss of nitrogen by the sale of crops and meat is 
seen to be far more considerable than the loss of phos- 
phoric acid or potash. The figures given are also below 
the truth, as they do not take into account the nitrates 
lost to the soil by drainage. Against this loss of nitrogen 
we have to place the amount annually supjDlied to the 
land by the rainfall, say 6 — 8 lbs. per acre, and also the 
unknown quantity absorbed as ammonia from the atmos- 
phere by soil and plant ; this latter amount will vary 
with the nature of the soil and climate, and probably 
also with the character of the cropping. We may, how- 
ever, safely assume that with the cropping and manuring 
supposed in the preceding table the total gain of nitrogen 
from the atmosphere will balance the loss, so that under 
good management the rotation might be indefinitely con- 
tinued without diminishing the fertility of the land. 

In the four-course manured rotation upon the heavy 
land at Rothamsted, the nitrogen annually removed in 
the crops, on an average of thirty-two years, has exceeded 
by about 35 lbs. the quantity supplied in the manure. 
If the crops on this experimental rotation should be per- 
manently maintained in quantity, of which at present we 
cannot be certain, we must conclude that this 35 lbs. of 
nitrogen, together with the unknown additional quantity 
lost as nitrate by drainage, have been annually derived 



KOTATIOK OF CROPS. 61 

from the atmosphere — partly as rain, but mostly by direct 
absorption by soil or crop. It appears very probable 
that on many soils the amount of nitrogen contributed 
by the atmosphere in the course of a rotation is very con- 
siderable. 

We have supposed that only grain and meat are sold off 
the land during the rotation ; it will often be economical 
to sell a larger part of the produce, and to purchase ma- 
nure in its place. The sale of straw will be attended 
with little practical loss on heavy land ; but on light land 
both the loss of potash, and the dimunition in the bulk 
of the manure will be more or less felt. The sale of 
hay or roots is far more exhaustive, and except on the 
most fertile soils, must demand a considerable purchase 
of manure or cattle food to replenish the soil with plant 
nourishment. 



CHAPTER VI. 
ANIMAL NUTRITION. 

The Constituents of the Animal Body. — Water, albuminoids, gelatin oids, 
horny matter, fat, and ash constituents — Composition of animals in 
various stages of growth and fattening — Proportion of carcass — 
Composition of increase whilst fattening. The processes of Nxitrition. 
— The constituents of food, and their particular functions in the 
body — Digestion — Respiration — Excretion. 

In order to understand the mode in which animals are 
nourished we must first obtain some acquaintance with 
the nature of the animal body, and understand the com- 
position of the increase which takes place during growth 
and fattening. 

. The Constituents of Animals. — The elements composing 
the animal frame are the ten already named as forming 
the essential constituents of plants (page 10), with sodium 
and chlorine in addition. The two last named elements 
are commonly present in the succulent parts of plants, 
but are apparently not essential to plant life — in the 
animal frame they are, however, indispensable. Fluorine 
and silicon are also always found in the animal body, but 
are not known to be essential for life or growth ; fluorine 
occurs in small quantities in the teeth and bones, and 
silicon in hair, wool, and feathers. 

The combustible matter of the animal body is mainly 
composed of nitrogenous substances, and of fat. 

The nitrogenous substances constituting the animal 
frame may be generally classed as — (1) albuminoids ; (2) 
gelatinoids ; and (3) horny matter. These three groups 
are related in composition, though differing a good deal 
in their properties. The albuminoids form the substance 
of animal muscle and nerve, and the greater part of the 
63 



ANIMAL JsTUTEITIOiT. 



63 



solid matter of blood ; they are, undoubtedly, of the first 
importance in tlie animal economy. The gelatinoids 
form the substance of skin and sinew, of all connective 
tissue, and also the combustible matter of cartilage and 
bone. Horny matter, named by chemists keratin, is the 
material of which horn, hair, wool, and feathers are con- 
stituted. 

The fats occurring in the animal body are principally 
stearin, palmitin, and olein. Stearin preponderates in 
hard fats, and olein in fluid fats. 

Of the incombustible constituents by far the largest 
part is contained in the bones. In fat animals 75 to 85 
per cent, of the total ash constituents are found in the 
bones. Bone ash chiefly consists of phosphate of calcium, 
with a small quantity of carbonate of calcium and phos- 
phate of magnesium. In muscle by far the most abun- 
dant ash constituent is phosphate of potassium. Potassium 
salts are also abundant in the ^^yolk " of unwashed wool. 
Blood, on the other hand, always contains a considerable 
quantity of sodium salts. 

The amounts of water, nitrogenous matter, fat, and 
ash constituents joresent in a large number of animals 
have been determined at Rothamsted. The following- 

o 

table shows the percentage composition of eight animals, 
after deducting the contents of the stomachs and intes- 
tines : — 



PERCENTAGE COMPOSITION OF WHOLE BODIES OF ANIMALS. 





Fat 
Calf. 


Half 
fat 
Ox. 


Fat 

Ox. 


Store Fat 
Sheep Sheep 


Extra 

fat 
Sheep 


Store 

Pig. 


Fat 
Pig. 


Water 


65.1 

15.7 

15.3 

3.9 


56.0 
18.1 

L^O.8 
5.1 


48.4 

15.4 

32 

4.2 


61.0 46.1 

15.8 13.0 

19.9 37.9 
3.3 ' 3.0 


37.1 

11.5 

48.3 

3.1 


58.1 

14.5 

24.6 

2.8 


43.0 

11.4 

43.9 

1.7 


Nitrogenous matter . . . 

Fat 

Ash 





The fat pig was one grown for fresh pork, not for bacon. 



64 



THE CHEMISTRY OF THE PARM. 



Water is in nearly every case tlie largest ingredient of 
the animal body ; the proportion of water diminishes 
with the growth of the animal, and especially durmg fat- 
tening. Fat forms in most cases the principal solid in- 
gredient of well-fed animals, its proportion increases very 
largely during fattening. The proportion of nitrogenous 
matter and ash tends to increase from youth to maturity, 
but diminishes during fattening. 

The largest proportion of nitrogenous matter and of 
ash are found in the ox, the smallest in the pig. The 
difference in the proportion of ash is chiefly due to the 
wide difference m the proportion of bone in these two 
animals. Fat is found in greatest quantity in the pig, 
and is least in the ox. 

The following table shows the quantity of nitrogen, 
and of the principal ash constituents, in the fasted live 
weight of the fat animals analyzed at Eothamsted. For 
convenience of comparison each animal is assumed to 
weigh 1,000 lbs. The table also gives the nitrogen and 
ash constituents in wool and milk ; it thus supplies full 
information as to the loss which a farm will sustain by 
the sale of animal produce. The composition of wool is 
mainly deduced from foreign analyses. 

ASH CONSTITUENTS AND NITROGEN IN 1,000 POUNDS OF 
VARIOUS ANIMALS AND THEIR PRODUCTS. 





Nitrogen. 


Phosphoric 
Acid. 


Potash. 


Linie. 


3Iag7iesia. 


jTai Ox 


23.18 
19.60 
17.57 
73.00 
6.40 


16.53 

11.29 

6.92 

1.00 

2.00 


1.84 
1.59 
1.48 
40.00 
1.70 


19.20 

12.80 

6.67 

1.00 

1.60 


0.63 
0.50 
0.35 
0.70 
0.20 


Fiit Sheep 

Fat Pig 


Wool, unwashed. 
Milk 





These figures show that the ox contains in proportion 
to its weight a large amount of nitrogen, and a much 
larger amount of phosphoric acid and lime, than either 



ANIMAL NUTRITIOIT. 



65 



the sheep or pig. Of all the animals raised on a farm the 
pig contains least of all the important ash constituents. 

The large amount of potash in unwashed wool is very 
remarkable ; a fleece must sometimes contain more potash 
than the whole body of a shorn sheep. 

In a fat ox about 60 per cent, of the fasted live weight 
will be butchers' carcass ; in a fat sheep about 58 per cent. ; 
m a fat pig (fatted for pork) 83 per cent. The proportion 
of carcass increases considerably during fattening. Thus 
the carcass in the store sheep killed at Rothamsted aver- 
age 53.4, in the fat sheep 58.6, and in the very fat sheep 
64.1 per cent, of the fasted live weight. 

When a lean animal is fattened the larger part of the 
increase in live weight is carcass. It was found at Roth- 
amsted that in the case of sheep passing from the " store" 
to the ''fat" condition, increasing in weight from 102 
lbs. to 155 lbs., about 68 per cent, of the increase was 
carcass. With *'fat" sheep passing to the ''very fat" 
state, increasing from 144 lbs. to 202 lbs. live weight, the 
proportion of carcass in the increase was about 77 per 
cent. With a fattening pig, increasing from 103 lbs. to 
191 lbs. live weight, the proportion of carcass m the 
increase was found to be 91 per cent. 

The percentage composition of the increase of sheep 
and pigs when passing from the "store" to the "fat" 
condition is about as follows. The increase of fattening 
oxen will have a similar composition. 

PERCENTAGE COMPOSITION OF THE INCREASE WHILST 
FATTENING. 





Water. 


Nitroqenous 
Matter. 


Fat. 


Ash. 


Sheep 


22.0 

28.6 


7.2 
7.8 


68.8 
63.1 


2.0 
0.5 


Pip-s 









The increase during the fattening stage of growth is 
thus chiefly an increase in fat, eight or nine parts of fat 



06 THE CHEMISTRY OF THE FARM. 

being laid on for one of nitrogenous matter. The pro- 
portion of fat would be somewhat greater still in the 
increase of highly fattened animals, as, for instance, of 
-pigs fed for bacon. 

The Processes of Nutrition. — We have already seen 
that the food of plants is of the simplest character. From 
such simple substances as carbonic acid, nitric acid, water, 
and salts, a plant is able to construct a great variety of 
elaborate compounds. It accomplishes these surprising 
transformations by a consumption of force ^(sunlight) 
external to itself. An animal has no such constructive 
power. The animal frame is built up of substances ex- 
isting ready formed in the food, or produced by the 
splitting up or partial combustion of some of the food 
constituents of the body. The animal also derives little 
or no aid from external force. The temperature of the 
animal (about 100° Fahr.) is maintained by the heat 
generated within the body from the combustion of the 
food consumed ; the force by which all the mechanical 
work of the animal is performed is also derived from the 
same combustion of food. The source of force m the 
animal is thus purely internal. 

It is evident from what has just been said that the food 
of animals has duties to perform which are not demanded 
of the food of plants. In plants the food merely pro- 
vides the matter for building up the vegetable tissues. In 
the animal, besides constructing tissue, the food has to 
furnish the means of producing heat and mechanical 
force. 

1. Food Constituents and their Functions.— The solid 
ingredients of animal food may be classed generally as — 
(1) albuminoids ; (2) fat ; (3) carbo-hydrates ; (4) incom- 
bustible matter, or ash. Besides these general ingredi- 
ents of food we have in immature vegetable products a 



ANIMAL KUTEITION". 67 

fifth class — the amides, which also take part in animal 
nutrition. The albuminoids and amides are nitrogenous 
substances, the other ingredients of food are non-nitro- 
genous. 

The various albuminoids occurring in grain, roots, and 
other forms of vegetable food, are quite similar in com- 
position to those found in milk, blood, and flesh. From 
the albuminoids of the food are formed not only the al- 
buminoids of the animal frame, but also the gelatinoids, 
the hair, wool, horn, etc., and to some extent the fat. 
By the combustion of albuminoids in the body, heat and 
mechanical force will also be developed. Albuminoids 
thus supply in themselves most of the requirements of 
the animal — a statement which can be made of no other 
food constituent. The albuminoids of food are frequently 
described in analyses as *^ flesh-formers." 

An animal, even when not increasing in weight, will 
always require a certain constant supply of albuminoid in 
its food to replace the waste of nitrogenous tissue which 
IS always going on ; the amount thus required is but 
small, in the case of an adult man at rest it amounts to 
about fifty grams (IV4 oz.) per day. 

When the nitrogenous tissues, or the albuminoids con- 
sumed as food, are oxidized in the body, the nitrogen 
they contain is not burned, but excreted m the form of 
urea. The urea produced is one-third the weight of the 
albumin oxidized. When the albuminoids, either of the 
food or of the wastmg tissues, are only partially oxidized, 
fat as well as urea may be produced. Theoretically, 100 
parts of albumin may yield 51.4 parts of fat. 

When amides are consumed as food they are burned in 
the system, and their nitrogen excreted as urea. Amides 
cannot supply the place of albuminoids as muscle-form- 
ers, but by combustion they serve for the production of 
heat and force. 

The fatty matter contained in food is similar to that 



68 THE CHEMISTKY OF THE EAKM. 

found in the animal body, but an animal is apparently 
capable of transforming one kind of fat into another. 
The fat of the food is either burned in the animal system 
to furnish heat and mechanical energy, or it is stored up 
as a reserve of force. Fat has a greater yalue as a heat 
and force-producer than any other ingredient of food. 

The carBo-hydrates of the food include starch, sugar, 
and cellulose ; these substances consist of carbon, hydro- 
gen, and oxygen, the last two elements being in the pro- 
portion to form water — hence the name. Various other 
non-nitrogenous constituents of food, as pectin, lignose, 
and vegetable acids, are also generally included under 
this title, though not strictly speaking carbo-hydrates. 
Carbo-hydrates form the largest part of all vegetable 
foods. They are not permanently stored up in the ani- 
mal body, but serve, when burned in the system, for the 
production of heat and mechanical work. They are also 
capable, when consumed in excess of immediate require- 
ments, of conversion into fat. 

Carbo-hydrates are of less value, for the same weight 
consumed, than either albuminoids or fat. Frankland 
found that 100 parts of fat when burned gave the same 
amount of heat and force as 211 parts of albumin (urea 
deducted), or 232 parts of starch. It is commonly reck- 
oned that 1 part of fat is equivalent to 2. 44 parts of starch. 
Cane sugar, according to the Eothamsted exi^eriments 
with pigs, has the same feeding value as starch. Cellu- 
lose, being more difficult of digestion, has probably a 
smaller value than either. 

The amides, carbo-hydrates, and fat, are quite incapa- 
ble of adding to the nitrogenous tissues of the body. They 
may, however, have this effect indirectly by protecting 
the albuminoids of the food from oxidation. A moder- 
ate quantity of albuminoids supplied to a growing animal 
will thus produce a larger increase of muscle when accom- 
panied by a supply of carbo-hydrates or fat than if con- 



ANIMAL NUTRITION". 69 

sumed alone. In the former case the non-nitrogenous 
ingredients of the food supply the heat and force de- 
manded by the animal body, in the latter case the albu- 
minoids have to meet every requirement. 

If an adult animal receives the small quantity of albu- 
minoids and ash constituents necessary to supply the 
waste of tissue, the whole of its remaining wants may 
probably be met by supplies of carbo-hydrates and of fat. 

The ash constituents present in the food are the same 
as those found in the animal body ; all that is accom- 
plished by the animal is to select from the supply those 
of which it is in want. 

2. Digestion.— The object of digestion is to bring the 
solid constituents of the food into a form suitable for ab- 
sorption into the blood. Of the carbo-hydrates of the 
food some, as sugar, are already soluble and diffusible, 
and need no digestion ; others, as starch and cellulose, 
are naturally insoluble. The digestion of carbo-hydrates 
commences with the action of the saliva, which has the 
property of converting starch into sugar. This action, in 
the case of ruminants, is prolonged by the temporary 
Bojourn of the food in the first two stomachs, and its re- 
turn to the mouth in chewing the cud. The further 
solution of starch and cellulose is effected in the intes- 
tines, partly by the pancreatic juice, which has a powerful 
action on starch, and partly by the fermentive processes 
which take place. 

The albuminoids of the food are attacked by the gas- 
tric juice of the stomach (the fourth stomach of rumi- 
nants), and converted into peptones, bodies similar to^al- 
buminoids in composition, but which, unlike them, are 
diifusible through a membrane. The pancreatic juice 
of the small intestines also converts albuminoids into 
peptones. 

Fat, liquefied by the heat of the body, is probably ca- 



70 THE CHEMISTRY OF THE FARM. 

pable of absorption without change. The digestion of 
fat in large quantities is greatly assisted by the bile and 
pancreatic juice. 

The absorption of the dissolved constituents of the 
food takes place more or less in all parts of the aliment- 
ary canal, but chiefly in the small intestines. The ab- 
sorbed matters pass into the blood. 

The blood of an animal is the source of nourishment 
to the whole body ; out of its ingredients all the tissues 
are formed. The blood is also the means of conveying 
the oxygen to the tissues which is essential to their vital- 
ity, and of removing from them carbonic acid, and the 
other products of their metamorphosis. 

3. Respiration. — The blood is supplied with oxygen 
during its passage through the lungs, where it is brought 
into contact with air. The oxygen is absorbed by the 
haemoglobin, which forms the chief constituent of the 
red corpuscles. The scarlet blood thus produced is cir- 
culated through the whole body by the arteries ; the 
oxygen it supplies is consumed in the tissues, producing, 
among other results, heat and mechanical work. The 
blood finally returns from the tissues by the veins. The 
haemoglobin has then lost oxygen, and has assumed a 
purple color ; the blood serum also contains carbonic acid 
gas in solution, and many other products of decomposition. 
By passing again through the lungs the carbonic acid is 
more or less completely discharged, and a fresh supply of 
oxygen obtained, 

4. Excretion. — The products which result from the 
oxidai ion of tissue, or of the food consumed, are removed 
from the body by the lungs, the kidneys, or the skin. 
The chief products of oxidation in the body are carbonic 
acid, water, urea, and salts. Carbonic acid is removed 
through the lungs, and to a smaller extent by the skin ; 



ANIMAL KUTRITIOK. 71 

urea and salts by the kidneys ; water by all the organs of 
excretion. 

Non-nitrogenous substances, as fat and sugar, when oxi- 
dized in the body, yield simply water and carbonic acid. 
The nitrogen of the albuminoids, gelatinoids, and amides 
is not oxidized, but is excreted in the form of urea. The 
sulphur of the albuminoids is apparently oxidized to sul- 
phuric acid. 

The quantity of nitrogen in the urine is a measure of 
the albuminoids, gelatinoids and amides oxidized in the 
body. In the urine are also removed all the salts not re- 
quired for the animal economy ; sodium and potassium 
salts are generally abundantly present. 

The solid excrement contains the undigested parts of 
the food, with the residues of the bile, and other secre- 
tions of the alimentary canal. 



CHAPTER VII. 
FOODS. 



The Composition of Foods.— Detailed. compositioD— Proportion of nitrogen 
existing as true albuminoids — Variation in foods due to age and 
manuring— Proportion between nitrogenous and non-nitrogenous 
constituents— Ash constituents. Digestibility of Foods.— Method of 
determination— Experiments with ruminants— Influence of age of the 
animal, daily ration, and labor— Influence of the maturity of fodder 
crops on their digestibility— Influence of one food on the digestibility 
of another— Common salt— Experiments with horses— Experiments 
with pigs— Experiments with geese. Comparative NutHtive Value 
of i^oocZs.— Influence of proportion of water- Comparative heat and 
work-producing power— Proportion of albuminoids to non-albumi- 
noids— General conclusions. 



In the preceding chapter we have enumerated the chief 
constituents of food, and described their functions in the 
animal body ; we may now proceed a step further, and 
consider the detailed composition and feeding value of 
the foods actually employed on the farm. 

The nourishing value of a food is plainly fixed by two 
factors : — 1. Its composition. 2. Its digestibility. The 
first of these determines the character of the food — its 
richness in albuminoids, fat, carbo-hydrates, and ash 
constituents. The second determines the extent to 
which these various constituents are made use of in the 
animal body. 

Composition of Foods. — The average percentage com- 
position of the foods commonly given to farm animals is 

72 



FOODS. 



73 



shown ill the following table. The figures given are in 
every case the mean of a large number of analyses. 



PERCENTAGE COMPOSITION OF ORDINARY FOODS. 



Cotton-Cake (decorticated). . . 
Cotton-Cake (undecorticated) 
Linseed-Cake 

Beans 

Peas 

Oats 

Wlieat 

Barley , 

Maize , 

Malt Dust , 

Wheat Bran , 

Brewer's Grains , 

Clover Hay 

Meadow Hay 

Bean Straw 

Wheat Straw 

Meadow Grass 

Green Clover 

Potatoes 

Mano;els , 

Swedes 

Turnips , 



1 


at2 


« 


Soluble 
Carbo- 
hydrates. 


^ 




10.0 
11.5 
13.0 


41.2 
24.6 

28.1 


14.0 

6.2 

12.0 


18.0 
30.2 
30.3 


9.0 
20.8 
11.0 


7.8 
6.7 
6.6 


14.5 
14.3 


25.5 
22.4 


1.6 
2.0 


45.9 

52.5 


9.4 
6.4 


3.1 

2.4 


13.0 
14.4 
14.0 
11.4 


12.9 
11.3 
10.6 
10.4 


6.0 
1.5 
2.0 
5.1 


53.8 
68.1 
63.7 

68.5 


10.8 
3.0 
7.1 
3.0 


3.5 
1.7 
2.6 
1.6 


9.5 
14.0 

77.4 


23.7 
14.2 

4.8 


2 2 
4^2 
1.4 


44.9 

50.4 

9.7 


12.5 

11.1 

5.3 


6.8 
6.1 
1.5 


16.0 
14.3 


12.3 

9.7 


2.2 

2.5 


38.2 
41.0 


26.0 
26.3 


5.3 

6.2 


16.0 
14.3 


6.3 
3.0 


1.0 
1.5 


36.7 
32.6 


35.0 
44.0 


5.0 
4.6 


80.0 
83.0 


3.5 
3.3 


0.8 
0.7 


19.2 
7.0 


4.5 

4.5 


2.0 
1.5 


75.0 
88.5 
89.3 
91.7 


2.1 
1.2 
1.5 
1.1 


0.3 
0.1 
0.2 
0.2 


20.5 
8.2 
7.3 
5.3 


1.1 
1.0 
1.1 
1.0 


1.0 
1.0 
0.6 
0.7 



The soluble carbo-hydrates in the above table include 
starch, pectin, and the finer parts of the fibre ; these are 
not soluble in water, but are dissolved by the weak acid 
and alkali employed by the analyst to separate the coarse 
fibre. 

The whole of the nitrogen present in the foods above 
mentioned has been reckoned as existing as albuminoids. 
We are obliged to adopt this usual mode of calculation for 
the sake of uniformity, the amount of true albuminoids 



74 THE CHEMISTRY OF THE FARM. 

having been determined only in the case of a few of the 
foods enumerated. 

It has been shown during the last few years that a part 
of the nitrogen in many foods exists, not as albuminoids, 
but as amides (e. g., asparagine and glutamine) and as 
nitrates. The subject is at present receiving the atten- 
tion of chemists. It appears that in seeds nearly the 
whole of the nitrogen exists as albuminoids, and this is 
especially true of the kernel of the seed. Thus in wheat 
flour about 90 per cent, of the nitrogen present is in the 
form of albuminoids, while in the bran which forms the 
skin of the grain only about 70 per cent, of the nitrogen 
is in this condition. For the various cakes and grains 
mentioned in the table the figures given for albuminoids 
will be approximately correct, but for the other foods 
the figures are undoubtedly too high. In hay it would 
appear, from the few determinations made, that about 80 
per cent, of the nitrogen is present as albuminoids. In 
malt-dust about 73 per cent, of the nitrogen is albuminoid. 
In potatoes about 60 per cent, of the nitrogen is in this 
condition. The few determinations made in swedes show 
about 45 per cent, of the nitrogen as albuminoids. While 
in mangels generally only about 25 23er cent, of the 
nitrogen is in this form. 

Tlie composition of all vegetable foods is liable to 
variation, depending on the state of maturity of the 
plant, and the character of the soil and season. In the 
case of perfectly matured produce, as, for instance, ripe 
seed, the variations in composition are not generally con- 
siderable, and an average composition, such as is given in 
the table, will be found in most cases pretty correct. But 
in the case of immature produce, such as meadow grass, 
turnips, or mangels, the composition largely depends on 
the stage of growth in which the plant is taken, and is 
also greatly affected by the character of the manuring. It 
may be generally stated that as a plant matures the pro- 



FOODS. 



75 



portion of water, nitrogenous matter, and ash constituents 
diminishes, while the proportion of carbo-hydrates largely 
increases. At the same time the amides become more or 
less converted into albuminoids. 

The following table shows the percentage composition 
of meadow grass cut at three different dates in the same 
field. The first cutting will represent pasture grass fed 
off in the green state by stock ; the second cutting is 
good ordinary hay ; the third cutting is an over-ripe hay, 
somewhat coarse and stemmy, but well harvested. The 
composition given in every case is that of the dry 
substance : — 



COMPOSITION OF HAT HARVESTED AT DIFFERENT DATES. 



Date of Cutting. 


Albumi- 
noids. 


Fat. 


Soluble 
Carbo- 
hydrates. 


Fibre. 


Ash. 


May 14 

June 9 

June 26 


17.65 

11.16 

8.46 


3.19 
2.74 
2.71 


40.86 
43.37 
43.34 


22.97 
34.88 
38.15 


15.33 

7.95 
7.34 



Young grass is thus much richer in albuminoids,* and 
contains a smaller proportion of indigestible fibre than 
older grass, and is consequently more nourishing. The 
same comparison may be made between young clover and 
that which is allowed to mature for hay. Hay should 
always be cut immediately full bloom is reached ; after 
this point the quality of the crop will considerably 
deteriorate. 

While fodder crops deteriorate towards maturity, from 
the conversion of soluble carbo-hydrates into fibre, crops 
such as potatoes and mangel improve, the carbo-hydrates 
produced in their case being respectively starch and sugar, 
both of them substances of great feeding value. 



* It must be borne in mind that in the present transition state of our 
analyses of food, the term " albuminoids " will generally include all the 
nitrogenous substances present. 



76 THE CHEMISTKY OF THE FAEM. 

The influence of high manuring is naturally to increase 
the luxuriance of a crop ; a luxuriant crop will always 
contain more water than one in less active growth. Very 
large mangels often contain only 6 per cent, of dry mat- 
ter, while in quite small roots the proportion may be as 
high as 15 per cent. Luxuriance also retards maturity. 
A heavily manured mangel will contain, at the same date, 
a much smaller proportion of sugar than a similar man- 
gel grown on poor soil. The result of high manuring is 
thus not only to increase the bulk of the crop, but also 
generally to diminish the proportion of carbo-hydrates, 
and increase the nitrogen, ash constituents, and water. 
In highly manured crops a smaller proportion of the nitro- 
gen will exist in albuminoids than in crops less heavily 
manured and more mature. 

In the case of hay the composition is further affected 
by the conditions of harvesting. Grass that has suffered 
from rain during haymaking will contain less soluble 
matter (carbo-hydrates and albuminoids) than well-made 
hay ; this loss will be greatly increased if the hay has 
been long in the field, and undergone fermentation as 
well as washing. 

Having pointed out the variations which are liable to 
occur, we may now consider the average composition of 
the various foods shown in the table. 

The amount of total dry matter is seen to be tolerably 
uniform throughout the various classes of dry foods, the 
foods richest in fat being generally the driest. In the 
green fodder and roots the proportion of water is gener-" 
ally very large ; potatoes contain the most, and white 
turnips the least proportion of dry matter. 

We have already seen that albuminoids and fat are the 
most concentrated forms of food which an animal can 
consume ; those foods which are rich in albuminoids and 
fat are therefore those which, generally speaking, have 
the highest nourishing value. At the head of all foods 



FOODS. 77 

in this respect stand tlie yarious descriptions of oil-cake ; 
they are, without doubt, among the most concentrated 
foods at the farmer's disposal. The leguminous seeds, as 
beans, peas, and lentils, are rich in albuminoids, but 
not in. fat. The cereal grains are much poorer in albu- 
minoids, containing only about one-half the proportion 
found in leguminous seeds. Of the common cereals, oats 
are generally the most nitrogenous, and maize the least. 
Oats and maize are characterized by containing more fat 
than the other cereal grains. The special characteristic 
of all the cereal grains is their richness in an easily 
digested carbo-hydrate, starch. 

Of the three cereal products mentioned in the table the 
bran and brewer's grains represent respectively the husk 
of wheat and barley. These foods are richer both in 
nitrogenous matter and fat, but contain a much more 
considerable proportion of fibre than the whole grain. 
Malt-dust (known also as malt-combs) consists of the 
radicles of the germinated barley, which are removed 
after the malt has been dried. This material is very rich 
in nitrogenous matter. 

When we turn to the hay, straw, green fodder, and 
roots, the general composition becomes a less safe guide 
to the nourishing value. The nitrogen, we have already 
seen, is here no certain measure of the proportion of albu- 
minoids present. The fat credited to these foods is also 
largely composed of waxy matters, and we can hardly at- 
tribute to it the same feeding value as to an equal amount 
of fat in oil-cake or maize. The carbo-hydrates also in- 
clude various substances of little or no feeding value. The 
same weight of dry matter in crude foods of this class has 
thus a decidedly less nourishing value than in foods con- 
sisting entirely of matured grain. Foods belonging to 
different classes cannot safely be compared on the basis 
of their composition. 

An important element in the character of a food is the 



78 THE CHEMISTRY OF THE FARM. 

proportion between its nitrogenous and non-nitrogenous 
constituents, these two classes of ingredients performing 
to a considerable extent distinct functions in the body. 
To find this proportion it is usual to calculate the fat into 
its equivalent in starch (generally done by multiplying 
the fat by 2.44), and add the product to the other carbo- 
hydrates of the food ; the relation of the albuminoids to 
the total non-nitrogenous constituents reckoned as carbo- 
hydrates is then easily found. The relation in question 
is commonly known as the " nutritive relation" of the 
food (Ntlhrstoffverhaltniss), but is better described as 
the '' albuminoid ratio." Thus the composition of wheat 
grain in the table shows an '^ albuminoid ratio" of 1 : 6.6, 
and the composition of decorticated cotton-cake an albu- 
minoid ratio of 1 : 1.5. Figures so calculated are, how- 
ever, only approximate, as we aught clearly only to take 
account of the constituents actually digested by the 
animal. We shall therefore refer to the subject again 
further on. 

Most foods supply a sufficient quantity of the ash con- 
stituents which are required for the formation of bone 
and tissue ; the chief of these are i^hosphoric acid, lime, 
and potash. 

The oil-cakes and bran are the foods richest in phos- 
phoric acid ; straw and meadow hay are the foods poorest 
in this constituent. Lime is most abundant in clover 
hay, bean straw, and turnips, and occurs in least quantity 
in the cereal grains and in potatoes. Potash is abundant 
in roots, hay, bean straw, bran, and oil-cake, and is found 
in smallest quantity in the cereal grains. 

Of all the ash constituents lime and soda are probably 
the most generally deficient. Maize is of all ordinary 
foods (rice excepted) the poorest in lime ; it certainly 
contains too small an amount for a rapidly growing 
animal. At Rothamsted a mixture of coal ashes, common 
salt, and superphosphate was used with advantage in the 



POODS. 79 

case of pigs fed solely on maize. It must be recollected, 
however, that animals will generally receive no inconsid- 
erable amounts of lime in their drinking water. 

The proportion of phosphoric acid and potash in vari- 
ous foods is shown in the table on page 111. 

Digestibility of Foods. — Our knowledge concerning 
the digestion of food by farm animals is almost entirely 
derived from German investigations ; * much information 
has already been obtained upon this subject, though a 
great deal yet remains to be accomplished. The general 
method of investigation has been to supply an animal 
with weighed quantities of food, the composition of which 
has been ascertained by chemical analysis. During this 
experimental diet the solid excrements are collected and 
weighed, and are finally analyzed by the same chemical 
methods previously applied to the food. Subject, there- 
fore, to contain small corrections for intestinal secretions, 
we obtain by this j)lan the amount of each constituent of 
the food which has passed through the animal unabsorbed, 
and by difference the amount digested. The proportion 
of each constituent digested for 100 supplied as food is 
known as its ''digestion coefficient." 

1. Experiments with Riiminafits.— Ruminating animals 
possess an extensive digesting apparatus, consisting of the 
well-known four stomachs, in addition to the intestinal 
organs. Food takes a considerable time in passing through 
this system. In changing the food of an ox five days will 
generally elapse before the remains of the preceding diet 
are expelled by the animal. Animals of this class are 
specially adapted for the digestion of bulky foods, con- 
taining much fibre. 



*The information ffiven in this section is taken almost entirely from 
the admirable work of Dr. E. Wolff, "Die Ernalirung der Landwirthaft- 
lichen Nutzthiere," with its valuable Supplement just published. 



80 



THE CHEMISTRY OF THE FARM. 



Experiments have been made with oxen, cows, sheep, and 
goats. The power of these different animals for digesting 
food is apparently very similar, but no accurate compari- 
sons haye as yet been made. The following table shows 
the average results obtained with ruminating animals fed 
on the foods respectively mentioned. The figures given 
represent the ' ' digestion coefficients " found for each con- 
stituent of the food consumed. The *^ albuminoid ratio " 
of the digested portion of the food is also given : — 

EXPERIMENTS WITH CATTLE, SHEEP, AND GOATS. 



;-' 

Food. 


Digested fw 100 of each C07ismuent 
supplied. 




lis 


1 "• 


1' 


Its 
3a| 


1 




Linseed Cake 


SO 
90 
71 
81 

88 
67 

59 
59 
59 
51 
46 
50 


84 
88 
79 

77 
79 

75 

56 
• 55 
76 
38 
20 
51 


90 

93 

84 

100 

85 
50 

47 
56 
38 
30 
36 
55 


78 
93 
76 
87 
91 
70 

62 
69 
07 
43 
39 
60 


? 

9 

24 

? 

9 

37 

57 
44 
40 
61 
56 
36 




L7 
2.1 
6.5 
8.2 
7.9 
4.5 

9.2 
: 6.2 
• 2.8 
:14.7 
:44.1 
: 6.2 


Oats 


*Barlev 


*Maize 


*Wheat Bran 

Meadow Hay 

Clover Hay 

Lucerne Hay 

Oat Straw 


* Wheat Straw 

*Bean Straw 



Roots and potatoes are not mentioned in the table ; 
they are apparently completely digested, with the excep- 
tion perhaps of the small amount of hard fibre contained 
in the epidermis and rootlets. 

The digestibility of the foods in the lower division of 
the table has been for the most part determined by feed- 
ing these animals on these foods alone ; the digestibility 



* These results are derived from one or two experiments only, 
t The numbers in this column refer to the foods actually used in the 
experiments. 



FOODS. 81 

of the foods in the upper division has been found by sup- 
plying them in various proportions along with hay, the 
digestibility of which has been already ascertained with 
the same animal. The amount of fibre in these last-named 
foods is usually too small for its digestibility to be deter- 
mined with certainty by a few experiments. 

The concentrated foods placed in the upper part of the 
table are seen to be far more thoroughly digested than 
is the case with hay or straw. When of good quality, 
80 or 90 per cent, of the organic matter of these foods 
will be assimilated by the animal, except in those cases 
where much fibre is present. The albuminoids and fat 
in these foods have especially a greater digestibility than 
the same ingredients in hay and straw. The hard fibre 
forming the husk of seeds is apparently but little diges- 
tible. The oats employed were of somewhat inferior 
quality. 

In the case of ordinary hay and straw the organic 
matter digested is but 45 to 60 per cent, of that supplied. 
The minimum amount digested occurs with wheat straw; 
oat straw, which is generally cut somewhat more green, is 
distinctly more digestible. The results given for meadow 
and clover hay relate to hay of average quality; the 
lucerne hay was of better quality, and shows a much 
higher degree of digestibility in the nitrogenous matter. 

The higher is the proportion of nitrogenous matter in 
hay and straw, the greater appears to be its digestibility. 
Thus the wheat straw experimented with contained 4.8 
per cent, of nitrogenous matter in its dry substance, of 
which only one-fifth, or 20 per cent. , was digested ; while 
good lucerne hay with 19.3 per cent, of nitrogenous 
matter, had 76 per cent, of this in a digestible form. The 
precise nature of the digested and undigested nitrogenous 
matter has not yet been ascertained ; amides being soluble 
bodies have probably been classed in these experiments 
as digestible albumin. 



82 THE CHEMISTRY OF THE FARM. 

Of the fibre in hay and straw about 40 to 60 per cent, 
is generally digested by ruminant animals. The fibre of 
leguminous hay and straw (clover and lucerne hay, and 
bean straw) is considerably less digestible than the fibre 
of similar graminaceous foods (grass hay, oat and wheat 
straw). It has been shown that both in the case of 
the soluble carbo-hydrates, and of the fibre, the portion 
digested has always the general formula of starch or 
cellulose, CgHj^O^, while the portion left undigested is 
much richer in carbon. It appears, therefore, that while 
cellulose is a digestible substance, the lignose which ic 
deposited in the tissues as the plant increases in age, and 
which contains a larger proportion of carbon, is indi- 
gestible. Chemical analysis shows that the fibre of 
leguminous hay and straw is richer in carbon, and conse- 
quently in lignose, than the fibre of grass hay, or grain 
straw. 

We must now glance at the circumstances which 
influence the proportion of food digested. The individual 
character of the animal undoubtedly affects the proportion 
digested. Of two animals supj^lied with the same food, 
one will often persistently digest a larger proportion than 
the other. In young animals the digestive power is 
apparently very similar to that of animals of full age. 
Sheep from six to fourteen months old showed no distinct 
change in digestive capacity. 

Differences in the quantity of the daily ration of hay 
do not sensibly affect the proportion digested ; an animal 
will not digest more by being starved. Labor also is 
practically without influence, horses at rest and at work 
digesting nearly the same proportion of their food. Dif- 
ferences in the quality of a food may, however, exercise a 
great influence on its digestibility ; the addition of 
another food may also considerably alter the rate of 
digestion of the first food. 

The digestibility of fodder plants is mainly determined 



FOODS. 



83 



by their age ; all tlie constituents of a young plant are 
more digestible than in the same plant of greater age. 
The composition of meadow grass cut at three dilferent 
dates has been already given on page 75 ; this grass was 
supplied to sheep in the form of hay, and yielded the 
following digestion coefficients : 

DIGESTION OF HAY BY SHEEP. 



Date of Cutting. 


Proportion of each co7istituent cigested for 
100 supplied. 


Total 
Organic 
Matter. 


Albumi- 
noids. 


Fat. 


Soluble 
Carbo- 
hydrates. 


Fibre. 


May 14 


75.8 
64.3 
57.5 


73.3 
72.1 
55.5 


65.4 
51.6 
43.3 


75.7 
61.9 
55.7 


79.5 
65.7 
61.1 


June 9 

June 26 



The diminution in digestibility with the increasing 
maturity of the grass is very striking, and is very equally 
spread over all the constituents. Similar experiments 
with clover cut at different stages of growth have yielded 
similar results. It follows plainly from what has been now 
stated that no fixed nutritive value can be applied to 
fodder crops, or to the hay made from them, as both tlieir 
composition and digestibility are largely influenced by 
their age and condition when cut. The young plant is 
always the most nutritive. 

The superior fattening quality of a pasture, as compared 
wdth that of the hay made from it, is clearly due to the 
fact that on land continually grazed the animal is entirely 
fed on young herbage, while hay will always consist of the 
fully grown plant. 

Fodder crops do not sensibly diminish in digestibility 
by being made into hay, if haymaking is carefully carried 
out in good weather. But the loss of the finer parts of 
the plant by rough treatment, or the washing out of 
soluble matter by rain, may considerably diminish the 



84 THE CHEMISTRY OF THE FARM. 

digestibility. Hay appears to lose some of its digestibility 
by keeping. 

We now turn the influence of one food on the digesti- 
bility of another. 

If to a diet of hay and straw, consumed by a ruminant 
animal, a pure albuminoid, as wheat gluten, be added, the 
added food is entirely digested without the rate of diges- 
tion of the original food being sensibly altered. The same 
result has been obtained in experiments with pigs. These 
animals were fed on potatoes, to which variable quantities 
of meat flour were afterwards added. The albuminoids of 
the meat were entirely digested, while the proportion of 
the potatoes digested remained unchanged. 

An addition of oil (olive, poppy, and rape oil) to a diet 
of hay and straw is also apparently without unfavorable 
influence on the rate of digestion ; indeed some experi- 
ments with small quantities of oil ('/^ lb. of oil per day 
per 1,000 lbs. live weight) show an improved digestion of 
the dry fodder. With large additions of oil the appetite 
of the animal for hay and straw is much diminished. 
Oil supplied in moderate quantities is itself entirely 
digested. 

An addition of starch or sugar to a diet of hay or straw 
diminishes its digestibility, if the amount added exceeds 
10 per cent, of the dry fodder. The albuminoids of the 
food suffer the greatest loss of digestibility under these 
circumstances ; the fibre also suffers in digestibility if the 
amount of carbo-hydrate added is considerable. When 
starch has been added, it is itself completely digested if 
the albuminoid ratio of the whole food is not less than 
1 :8.* 

These facts are of considerable practical importance. 



* In this statement made by Wolff the whole of the nitrogen in the 
food is reckoned as albuminoid. 



FOODS. 85 

Nitrogenous foods, as oil-cake and bean meal, may be given 
with hay and straw cha2 without affecting their digesti- 
bihty ; but foods rich m carbo-hydrates, as potatoes and 
mangels, cannot be given in greater proportion than 15 
per cent, of the fodder (both reckoned as dry food) with- 
out more or less diminishing the digestibility of the latter. 
This decrease in digestibility may, however, be couuter- 
acted in great measure by supplying with the potatoes or 
mangels some nitrogenous food. When this is done the 
proportion of roots of potatoes may be double that just 
mentioned without a serious loss of digestibility. Potatoes 
exercise a greater depressing effect on the digestibility of 
hay than roots, starch being more potent in this respect 
than sugar. The cereal grains are rich in starch, but 
contain also a fair proportion of albuminoids ; they may 
be added to dry fodder without seriously affecting its 
digestibility, if the albuminoid ratio of the whole food 
does not fall below 1:8.* 

Common salt is well known to be a useful addition to 
the food of animals. It does not apparently assist diges- 
tion, but it increases appetite ; and when sodium salts 
are deficient in the food, it supplies the blood with a 
necessary constituent. Sodium salts are tolerably abun- 
dant in mangels, and small in quantity in hay ; they are 
absent in potatoes, and generally absent in grain of all 
kinds. 

2. Experiments with Horses.— In recent experiments 
conducted by Wolff the digestive powers of horses and 
sheep have been accurately compared, the same food 
having been supplied to each set of animals. 



* In tWs statement made by Wolff tlie whole of the nitrogen in the 
food is reckoned as albuminoid. 



86 



THE CHEMISTRY OE THE FARM. 



The principal results were as follows : — 

EXPERIMENTS WITH HORSES. 



Food. 


JProportion of each constituent digested 
for 100 supplied. 


Total 
Organic 
Hatter. 


Albumi- 
noids. 


Fat. 


Soluble 
Carbo- 
hydrates. 


Fibre. 




62.1 
51.7 
46.3 
57.9 
72.0 
87.4 
90.9 


68.8 

64.3 

58.4. 

74.3* 

87.0 

86.2 

77.6 


13.4 
23.5 

18.8 
3.2 

78.2 
8.5 

63.0 


65.8 
56.9 
51.7 
70.2 
76.6 
93.4 
93.9 


57.0 
42.6 
37.3 
39.0 
25.6 
69.3 
100.0 


Meadow Hay (very good) 
Meadow Hay (ordinary). 
TjIippttir TTnv . ... 


Oats 




JMaize 





EXPERIMENTS WITH SHEEP. 



Pasture Grass 

Meadow Hay (very good) 
Meadow Hay (ordinary). 

Lucerne Hay 

Oats 

Beans 

Maize 



75.8 


73.3 


65.4 


75.7 


79.5 


64.7 


66.6 


54.5 


65.6 


63.5 


58.7 


57.2 


44.3 


58.7 


59.8 


59.1 


72.8 


29.7 


67.9 


43.6 


72.9 


85.5 


84.8 


77.7 


26.1 


89.6 


87.1 


84.2 


91.2 


78.5 


88.5 


78.5 


84.6 


91.3 


61.9 



On comparing these figures it is evident that a horse 
digests meadow grass and hay less perfectly than a sheep, 
and the difference between them is apparently as great 
when the food is young grass as when ordinary hay is 
employed. There is little difference m the proportion of 
albuminoids assimilated by the two animals, but the 
divergence becomes very considerable when we come to 
the carbo-hydrates, fibre, and fat. Of the carbo-hydrates 
the horse digests 7 — 10 per cent., of the fibre 22 per cent., 
and of the fat and waxy matter 25 — 52 per cent, less than 
the sheep. On the whole, the horse digests about 12 per 
cent, less of the total organic matter of grass hay than 
the sheep. With lucerne hay of good quality the digestion 
by the horse is far better, and (save as regards the fat) 
nearly equals that of the sheep. 

The small digestive power of the horse for vegetable 



FOODS. 



87 



fibre is plainly connected with the fact that it is not like 
the sheep a ruminant animal, and is thus uujDrovided 
with the same means of attacking an insoluble food. In 
a trial with wheat-straw chaff the horse digested 22.5, 
and the sheep 47.6 per cent, of the total organic 
matter. 

With grain the digestion of the horse is apparently quite 
equal to that of the sheep. The beans and maize were 
soaked in water before they were given to the horse. 
Stress must not be laid on the digestion coefficients found 
for ingredients of the food present in small quantity, as 
for instance, the fat and fibre of beans, and the fibre of 
maize. 

3. Experiments with Pi^s. — These have not been so 
numerous as those with ruminant animals. The followino- 

o 

table shows the digestibility ascertained for some of the 
common pig foods : — 

EXPERIMENTS WITH PIGS. 



Food. 


Digested for 100 supplied. 


Albumi- 
noid 
ratio, f 


Total 
Organic 
Matter. 


A Ihiimi- 
noids. 


Fat. 


Soluble 
Carbo- 
hydrates. 


*SourMilk 

*Meat Flour 


97 
93 
91 
84 
84 
91 
67 
94 


96 
97 

88 
79 
■ 79 
84 
66 
81 


95 
87 
58 
71 
70 
76 
58 


99 

97 
91 
90 
94 

75 
98 


1:2.3 
1 :0.4 
1 :2.5 
1 :2.6 
1 : 7.0 
1 :8.8 

l':*9.'2 


Pea Meal 


Bean Meal 


*Barley Meal 

Maize Meal 

Rye Bran 


Potatoes 





The digestive power of the pig for the foods here 
mentioned is very considerable, and in cases admitting of 
comparison appears to be fully equal to that possessed by 



* The numbers in this case are the result of a single experiment. 
+ These ratios refer to the part of the food actually digested. 



88 THE CHEMISTRY OP THE FARM. 

ruminant animals. Nor is the pig incapable of digesting 
vegetable fibre, when this is presented in a favorable 
condition. Two pigs fed on green oats and vetches 
digested 48.9 per cent, of the fibre supplied. The diges- 
tive apparatus of a pig is not, however, adapted for dealing 
successfully with bulky fodder. Pigs are very capable of 
digesting animal food. 

4. Experiments with Geese. — These birds have no 
power of digesting vegetable fibre ; the food apparently 
passes too quickly through the system for the fibre to be 
attacked. 

Comparatiye Nutritive Value of Foods, — Having 
made ourselves acquainted with the comjDosition and 
degree of digestibility of the ordinary cattle foods, we 
may now offer some general considerations as to their 
relative feeding value. 

1. Influence of proportion of Water. — The feeding 
value of roots, and of other foods rich in water, is often 
diminished by the fact that a part of the heat they pro- 
duce in the body is consumed in raising the water they 
sujDply to the temperature of the animal, and of vaporizing 
a part of it as perspiration. With sheep the normal 
proportion of water to dry food is about 2:1; with 
cattle from whose skin perspiration is more active, about 
4: 1. 

A sheep feeding on turnips in winter in the open field, 
consuming, say, 20 lbs. of roots per day, will receive in its 
food about 18 lbs. of water of which 14 lbs. is beyond that 
necessary for nutrition. This 14 lbs. of water has to be 
raised from near the freezing point to the temperature of 
the animal body, a rise of at least 60° Fahr. To warm 
the water to this extent will require the combustion of 
about 54 grams of carbo-hydrates, reckoned as starch. 



FOODS. 89 

equal to about 6 per cent, of the total food consumed. 
The actual waste of food will, however, considerably 
exceed this, as a part of the extra water will be vaporized 
as perspiration, and to vaporize 1 lb. of water at the 
temperature of the animal body requires the combustion 
of 62 grams of starch. The consumption of an excess of 
water will also slightly increase the amount of albuminoids 
oxidized in the animal body, and thus occasion a certain 
amount of waste of the nitrogenous part of the food. 

The economy of supplying sheep on roots or green fodder 
with dry food in addition is obvious from the facts just 
stated ; by so doing the quantity of water consumed by 
the animal is diminished, and its proportion in the diet 
brought more nearly to a normal ratio. 

2. Capacity for producing Heat and Work.— The 

only basis on which the nutritive value of foods of 
different composition can be compared is in respect to 
their capacity for producing heat. The production of 
heat and mechanical work is the principal result which 
food accomplishes in the animal body ; the capacity for 
producing heat also stands in a near relation to the 
capacity for producing fat. On the other hand, the 
amount of heat which any food is capable of producing 
stands in no relation to its power of increasing or renew- 
ing the nitrogenous tissues of the body. We may, how- 
ever, safely assert that the amount of heat generated by 
the combustion of the digestible constituents of any food 
will be a fair guide to its nutritive value, when the diet 
of which it forms a part supplies a sufficient amount of 
digestible albuminoids, and this will be the case whenever 
foods are skillfully used. 

According to Frankland's actual determinations of the 
heat-producing power of fat, albumin, and starch, their 
comparative values in this respect are 100, 47.4, and 43.1. 
The albumin is here reckoned as minus its equivalent 



90 



THE CHEMISTRY OF THE FARM. 



quantity of urea, as this product of the decomjiosition of 
albumin is not burned, but excreted by the kidneys. If, 
now, we take the proportions of digestible fat, albu- 
minoids, carbo-hydrates and cellulose, supplied by any 
food, and multiply them by the heat coefficients just giveu^ 
the sum of the products will represent the heat-proflucing 
capacity of the food when consumed in the animal body. 
Taking the heat-producing capacity of maize, calculated 
in this manner, as 100, the values found for other foods 
will be as follows : — 

COMPARATIVE HEAT-PRODUCING VALUE OF FOODS. 



Ordinary 




condition. 


Jrerjecuy 


100 


100 


95 


96 


93 


96 


85 


88 


80 


81 


67 


69 


59 


61 


47 


49 


30 


105 


13 


100 



Maize 

Linseed Cake 

Beans 

Barley 

Oats 

Wheat Bran . . 
Meadow Hay. 
Wheat Straw. 

Potatoes 

Mangels 



These figures are to be taken only as approximations to 
the truth ; their correctness mainly depends upon the 
accuracy of the digestion experiments with ruminant 
animals described in the last section. The figures given 
for those foods containing amides, and salts of organic 
acids, are undoubtedly too high. Linseed cake, from the 
large proportion of fat and albuminoids which it contains, 
would be expected to occupy a much higher position in 
the table ; its lower rank is due to its imperfect digesti- 
bility. The table on page 80 shows that while 20 per 
cent, of linseed cake remains undigested, and therefore 
useless to the animal, only 12 per cent, of maize, and 10 
per cent, of beans are thus wasted. 

The general result is to show that the heat and work- 
producing power of the more perfectly digested food is 



FOODS. 



91 



nearly equal, if we assume the same quantity of dry food 
to be supplied in eacli case. 

We aliould gather from these calculations that an equal 
weight of maize, beans, or linseed cake will have nearly 
similar feeding value if supplied to an animal receiving a 
sufficient amount of albuminoids in its diet, as for exam- 
ple if given to a sheep fed on good meadow or clover hay. 



3. Proportion of Albuminoids to Non°A!buminoids. — 

A further point of great importance in determining the 
value of a food is the proportion between the digestible 
albuminoids, and the digestible non-nitrogenous constitu- 
ents : this relation we have already termed the ^^albu- 
minoid ratio " of the food. In calculating this relation 
the whole of the non-nitrogenous ingredients of the food 
are first reduced, as already explained, to their equivalent 
in starch. Taking the average composition of foods 
already given, and the digestibility of their constituents 
shown by the German experiments, the albuminoid ratios 
will be as under : — 

PROPORTION OF NITROGENOUS TO NON-NITROGENOUS CON- 
STITUENTS IN THE DIGESTIBLE PART OF FOOD. 



Total 

rec 


Nitrogen, 
koned. 


Amides, etc., not 
reckoned. 


Cotton Cake, decorticated 1 

Cotton Cake, un decorticated 1 

Linseed Cake . 1 


L5 

1.8 
2.3 
2.4 
2.9 
4.2 
5.5 
7.6 
9.0 
5.9 
8.0 
5.9 
6.2 
8.0 
10.6 
64.4 


1 *:" ' 7.0 

9 

1 :'l2.4 
1 : 13.1 

9 

1 :'31.8 
1 : 17.7 

? 


Beans 1 


Peas 1 


Wheat Bran 1 


Oats 1 


Barley 1 


Maize 1 


Clover Hay 1 


Meadow Hay 1 


Swedes 1 


Turnips. 1 


Mangels 1 


Potatoes 1 


Wheat Straw 1 





92 THE CHEMISTRY OF THE FARM. 

In the first column the whole of the nitrogen in the 
food is reckoned as existing as albuminoids ; in the second 
column the true albuminoids only are taken account of. 
In calculating the second column it has been assumed 
that in a digestion experiment the amides and nitrates, 
being soluble bodies, would be reckoned as '^ digestible 
albumin ;" the amides have not, howeyer, been reckoned 
among the non-albuminous constituents, their equivalent 
in starch not being yet known. 

The figures show in a striking manner the wide differ- 
ences that exist among foods as to the proportion of albu- 
minoids which they supply, the difference being made still 
more considerable by the recent discovery that a large 
part of the nitrogen in certain foods exists as amides 
and not as albuminoids. Mangels now appear as a food 
very poor in albuminoids, whereas they were formerly 
supposed to supply a sufficient proportion ; and the same 
is doubtless true of other roots not yet thoroughly ex- 
amined. 

The poverty of a diet of roots and straw chaff in diges- 
tible albuminoids is the true reason of the excellent effects 
produced by the addition of oil-cake or leguminous grain. 
Oil-cake and beans used under these circumstances have an 
effect far above their own intrinsic feeding value, as their 
presence raises the character of the whole diet, and ena- 
bles the carbo-hydrates of the roots and straw to contrib- 
ute to the formation of carcass. 

It must be recollected that the albuminoid ratio of a 
food may be different for different animals if their pow- 
ers of digestion are unequal. Thus the same meadow hay 
supplied to sheep and horses had for the former an albu- 
minoid ratio of 1 : 9.1, and for the latter a ratio of 1 : 6.7 
The horse, as we have seen, digests the nitrogenous con- 
stituents of hay nearly as well as the sheep, but fails in 
digesting the non-nitrogenous constituents. Hay is thus 
a more nitrogenous food for horses than for sheep. 



FOODS. 93 

The proportion of albuminoids most suitable for various 
diets will come under consideration in the next chapter. 

General Conclusions. — We have now run through the 
principal points which determine the value of food. A 
little consideration, will, however, show that it is impos- 
sible to affix a definite feeding value to any food, as its 
practical effect must depend in great measure on the con- 
ditions under which it is employed ; more especially on the 
kind of animal consuming it, and the general character 
of the diet of which it forms a part. Thus, the value of 
a bulky food, as hay or straw, is far greater when given to 
a ruminant animal, than when consumed by a horse or 
pig. Concentrated, easily digestible foods, as grain and 
oil-cake, have clearly a value above their composition when 
added to a poor and bulky food, as straw chaff, or to a 
watery food like turnips, because they are the means of 
raising the diet to a point at which an animal will thrive. 
On the other hand, roots and green fodder, even when 
Avatery and poor in composition, may have a considerable 
effect when added in moderate proportion to dry food. 
The highest value is, in short, only obtained from food 
when it is skillfully employed. 

There is, finally, a condition which we can never hope 
to express by figures, but which has a considerable influ- 
ence on the effect of any diet ; this is flavor. An agreeable 
flavor stimulates appetite, and probably promotes diges- 
tion. This part of the question belongs, however, rather 
to practice than science. 



CHAPTER VIII. 

EELATION OF FOOD TO ANIMAL EEQUIREMENTS. 

The Requirements of the Young Animal. — Composition of colostrum and 
milk — Suitable albuminoid ratio of the food. The Adult Animal. — 
Work, how performed — Maintenance diets — Labor diet. The Fatten- 
ing Animal. — Conditions necessary for increase — Results obtained 
when fattening oxen, sheep, and pigs, on ordinary diets — Alterations 
in consumption of food, and rate of increase, as fattening proceeds 
— Albuminoid ratios for fattening animals. Production of Wool. — 
Composition of wool— Influence of diet. Production of Milk. — Influ- 
ence of diet on the quantity and quality of the milk — Influence on 
the character of the butter— Albuminoid ratio for milk-cows. 

The Youn,i? Growing Animal. — The special character 
of the nutrition of young animals is the rapid formation 
of nitrogenous tissue and bone, for which purpose an 
abundant supply of albuminoids and ash constituents in 
the food is clearly requisite. 

The kind of food most appropriate to the wants of a 
young animal is shown by the consumption of milk. The 
milk supplied to the young immediately after birth (the 
colostrum) is of a very concentrated description. During 
the first week after birth the quantity of the milk greatly 
increases, and its composition gradually alters from that 
of colostrum to that of ordinary milk. 

In the following table will be found the composition of 
the colostrum and milk yielded by various farm animals ; 
the numbers given are the mean of many analyses. 
94 



EELATIOK OF FOOD TO AKIMAL REQUIREMENTS. 95 
COMPOSITION OF COLOSTRUM. 





Water. 


Albumi- 
noids. 


Fat. 


Sugar. 


Anil. 


Albuminoid 
ratio. ^- 


Ewe.... 
Sow .... 
Cow .... 


73.2 
70.1 

71.7 


15.4 
15.6 

20.7 


2.0 
9.5 
3.4 


8.0 
3.8 
2.5 


1.4 
0.9 

1.8 


1 : 0.8 
1 : 1.7 
1 : 0.5 



COMPOSITION OF MILK. 



Ewe.... 

Sow .... 
Goat . . . 
Cow.... 

Ass 

Mare . . . 


83.1 
84.6 

85.3 
87.0 
90.0 
90.4 


5.5 
6.3 
4.1 
4.0 
2.3 
2.0 


5.5 
4.8 
5.2 
3.7 
1.3 
LO 


5.0 
3.4 
4.6 
4.6 
6.0 
6.2 


0.9 
0.9 
0.8 
0.7 
0.4 
0.4 


1 : 3.3 
1 : 2.3 
1 : 4.1 
1:83 
1 : 3.7 
1 : 4.0 



The colostrum is characterized by an especially high 
percentage of albuminoids. In milk we find a smaller 
proportion of albuminoids, and a larger proportion of fat 
and sugar. The solid matter of milk has a very high 
feeding value, owing to the large proportion of fat and 
albuminoids present, and its perfect digestibility. If we 
take, as before, the heat-producing capacity of dry maize 
at 100, then the heat-producing capacity of dry cow' s 
milk will be 140. Milk also supplies the ash constituents 
necessary for the formation of bone and tissue : 100 lbs. 
of cow's milk will supply about 0.20 lb. of phosphoric 
acid, 0.16 lb. of lime, and 0.17 lb. of potash. 

The relation of the nitrogenous to the non-nitrogenous 
constituents of milk is much higher than in most vegeta- 
ble foods ; the analyses in the table show a relation vary- 
ing from 1 : 2.3 to 1 : 4.1, and the latter proportion is 
seldom much exceeded in any sample of milk. In sup- 
plying very young animals with artificial food the above 
facts must be borne in mind ; the food should clearly be 
of an easily digestible character, and contain a con side ra- 



* In calculating this relation it has been assumed that 10 of milk 
sugar are equivalent to 9 of starch. 



96 THE CnEMISTRY OF THE FARM. 

ble proportion of albuminoids and fat. Instead of this, 
foods rich in starch are too often employed. Linseed is 
perhaps, of ordinary foods, the one most similar to milk 
in composition. 

As the animal grows the quantity of food it requires 
increases, at the same time a larger proportion of the 
food is applied to the production of heat and mechanical 
work ; the proportion of nitrogenous matter in the food may 
therefore gradually be diminished, carbo-hydrates and fat 
being quite as fit as albuminoids for producing heat and 
work. Under natural conditions this diminution in the 
nitrogenous character of the diet soon takes place, the 
animal daily taking more and more grass in addition to 
its mother's milk. The albuminoid ratio * of the diet of 
rapidly growing animals may vary from 1 : 5 to 1 : 7, the 
more nitrogenous diet being most suitable for younger 
animals, or for the production of more rapid increase. 

The adult Animal • — Food, we have already seen, is 
primarily employed for the renovation of the animal 
tissues, and for the production of heat and mechanical 
work ; by far the greater portion of the food is applied to 
the latter purposes. 

Much of the work performed by an animal is internal, 
and consists in the muscular movements which produce 
circulatioD, respiration, and other vital processes ; such 
work is carried on even when the animal is at rest. In 
man the whole of the blood is pumped through the heart 
every half minute. The daily work performed by the 
heart of an average man has been calculated as equal to 
150 — 200 foot-tons ; that is to say, the power exerted by 
the heart would raise 1 ton to the height of 150 — 200 feet. 
The work performed by other organs, and by the muscles 



* The albuminoid ratios henceforward ffiven will represent, as far as 
possible, the proportion of true albuminoids present in the food. 



RELATIOI^ OF FOOD TO A2!?^IMAL REQUIEEMEl^TS. 97 

when merely maintaining the body in the erect position, 
has not yet been satisfactorily measured. 

It was formerly supposed that muscular force was 
produced by the oxidation of the muscle, and that a diet 
rich in albuminoids was consequently necessary if hard 
labor was to be maintained. This idea is now known to 
be erroneous, it having been shown by repeated experi- 
ments that labor does not necessarily increase the pro- 
duction of urea, while it does in every case greatly aug- 
ment the amount of carbonic acid and water exhaled. 
Mechanical power is, in fact, produced not by oxidation 
of the muscle, but of the organic matter in circulation ; 
this organic matter may be indifferently either fat, carbo- 
hydrates, or albuminoids. The animal food thus obtains 
the power necessary for the performance of work in the 
same manner as a steam engine, only that in the body 
food is burned in the place of coal. 

When labor is demanded from an under-fed animal, 
the oxidation taking place in the circulatory system may 
be in excess of the food supplied, and of the fat and car- 
bo-hydrates in circulation ; in such a case the albuminoids 
of the animal body are oxidized, and the excretion of urea 
becomes increased. A working animal ill-supplied with 
food will thus suffer seriously in condition. 

In the case of an adult animal not increasing in weight, 
and performing a minimum amount of work, as, for 
instance, a horse or ox in a stable, the quantity of food 
required is reduced to its smallest limits. An ox of 1,000 
lbs. live weight, quiet in the stall, will require daily, ac- 
cording to the German experiments, about 0.5 — 0.6 lb. of 
digestible albuminoids,* and 7.1 — 8.4 lbs. of digestible 
non-albuminous food, reckoned as starch, to preserve its 
condition. With sheep the maintenence diet must be 
more liberal, as in their case the growth of wool, with its 

* These numbers represent true albuminoids, and are, therefore, 
smaller than the German figures. 



98 THE CHEMISTRY OF THE FAEM. 

accompanying fat, is always in progress, and is practically 
independent of the abundance or poverty of the diet. 
Eor 1,000 lbs. live weight (shorn), sheep fed on meadow 
hay will require about 0c9 lb. of digestible albuminoids, 
and 10. 8 lbs. of digestible non-albuminous food, or 16 — 17 
lbs. dry organic matter, per day, to preserve their con- 
dition. If fed on mangels and straw chaff the quantity 
of dry organic matter must be raised to 20 — 25 lbs. In 
these maintenance diets for adult animals the albuminoid 
ratio of the food is but 1 : 14 in the case of the ox, 1 : 12 
in the case of the sheep fed on hay, and the relation is 
wider still in the case of the sheep fed on straw and man- 
gels. The inferiority of the latter diet is the cause 
doubtless of the larger amount of food required. 

If external work is to be performed, the body weight 
remaining unaltered, the quantity of food must be consid- 
erably increased, and the food must be of such quality 
that it may be possible to digest a sufficient amount in 
the required time. A man doing a fair day's work was 
found to exhale one-third more carbonic acid than when 
at rest ; a man doing such work would clearly require 
one-third more food to maintain the same condition of 
body. 

If we assume that when food is burned in the body one- 
fifth of the energy developed may appear as external 
work, then 1 lb. of digested starch would enable an 
animal to perform 485 foot-tons of work, 1 lb. of digested 
albumin 528 foot-tons, and 1 lb. of digested fat 1,127 
foot-tons of work. 

The recent experience of the use of maize for horses 
shows that an albuminoid ratio of 1 : 9 is quite sufficient 
for a labor diet. 

The Fattening Animal. — The character of the fatten- 
ing process has been more thoroughly studied than the 
nutrition of young and growing animals. 



RELATION OF FOOD TO AKIMAL REQUIREMENTS. 99 

For the body to increase in weight it is clear that the 
food supplied must be in excess of the quantity demanded 
for mere renovation of tissue, and for the production of 
heat and work. When such an excess of food is given, a 
part of the albuminoids and ash constituents is generally 
converted into new tissue, while a part of the fat, carbo- 
hydrates, and albuminoids is stored up in the form of fat. 
As only the excess of the food is converted into increase, 
liberal feeding is, within certain limits, the most econom- 
ical. If a lamb can be brought by liberal treatment to 
150 lbs. live weight at one year old, the amount of food 
consumed will be far smaller than if two years are occu- 
pied in attaining the same weight, for the food required 
for animal heat and work durmg the second year is 
clearly saved. 

Economy of food is also promoted by diminishing the 
demand for heat and work. An animal at rest in a stall 
will increase in weight far more than an animal taking 
active exercise on the same diet. In the same way the 
increase from a given weight of food will be less in winter 
than in spring or autumn, a far larger proportion of the 
food being consumed for the production of heat when the 
animal is living in a cold atmosphere. Hence the econo- 
my of feeding animals under cover during winter. If, 
however, the temperature becomes so high as to consider- 
ably increase the perspiration, waste of food again takes 
place, heat being consumed in the evaporation of water. 
The temperature most favorable for animal increase is 
apparently about 60° Fahr. Quietness, and freedom from 
excitement are essential to rapid fattening ; the absence 
of strong light is therefore desirable. 

The capacity of an animal for fattening depends much 
on breed and temperament, A farmer learns to recognize 
the fattening disposition of an animal from the feel of its 
skin, etc. 

The three animals with which the farmer is chiefly 



100 



THE CHEMISTRY OF THE PARM. 



concerned have very different powers of consuming food, 
and yield different rates of increase. Lawes and Gilbert 
reckon that, on an average of the whole fattening period, 
an ox will produce 100 lbs. of live weight from the con- 
sumption of 250 lbs. oil-cake, 600 lbs. clover hay, and 3,500 
lbs. swedes. Sheep will produce the same increase by the 
consumption of 250 lbs. oil-cake, 300 lbs. clover hay, and 
4,000 lb. swedes. Pigs will require about 500 lbs. of 
barley meal to yield a similar result. Taking these data, 
the rate of food consumption, and of increase yielded will 
be as follows : — 

KESULTS OBTAINED WITH FATTENING ANIMALS 
PER 100 LBS. LIVE WEIGHT PER WEEK. 



Oxen . 
Sheep . 
Pigs.. 



Beceived by the 
animal. 



Total 

Dry 

Food. 



lbs. 
12.5 
16.0 
37.0 



Results produced. 



Food 
Digestible consumed 



Organic 
Matter. 



lbs. 

8.9 

12.3 

22.0 



for heat 

and 
woi'k.* 



lbs. 

6.86 

9.06 

12.58 



Dry 

Manure 

pro- 
duced.-f 



lbs. 
4.56 
5.10 
4.51 



Increase 
in live 
weight. 



lbs. 
1.13 
1.76 
6.43 



RESULTS OBTAINED IN RELATION TO FOOD CONSUMED. 



Increase in live 
weight. 



Rr 

100 lbs. 
Dry 

Food. 



On 100 lbs. of Dr-y Food. 



Per 
100 lbs, 

Digested Jeafand 
Orr/ajiic ^y^fc* 
Matter. 



Con- 
sumed for 



Dry 
Ifanure 

pro- 
duct d.f 



Dry 

Increase 
yielded. 



Oxen . 
Sheep. 
Pigs.. 



lbs. 

9.0 

11.0 

23.8 



lbs. 
12.7 
14.8 
29.2 



lbs. 
54.9 
56.6 
46.6 



lbs. 
36.5 
31.9 
16.7 



lbs. 
6 2 
8.0 

17.6 



* In calculating the amount of food consumed for the production of 
heat and work, it has been assumed that the fat in the increase has been 
derived entirely from the fat and carbo-hydrates supplied by the food. 

t The manure is exclusive of litter. 



EELATIOK OF FOOD TO AN"IMAL KEQUIREMEKTS. 101 

It is evident from the upper division of the table that 
pigs are able to consume far more food in proportion to 
their weight than either sheep or oxen. This is due to 
the concentrated and digestible character of the food 
(barley meal) supplied to a fattening pig, and- to the great 
capacity of this animal for assimilation. The proportion 
of stomach is greater in a fat ox or sheep than in a pig, 
being on 100 lbs. live weight, 3.2 for the ox, 2.5 for the 
sheep, and 0.7 for the pig. On the other hand, the 
proportion of the intestines is greater with the pig than 
with sheep or oxen. Euminant animals are thus best 
fitted for dealing with food requiring a prolonged 
digestion, while the pig excels in the capacity for assimi- 
lation. 

As a natural result of the larger consumption of food 
the pig increases in weight nr.ucli more speedily than 
either the sheep or ox ; but not only is the rate of 
increase more rapid, the increase yielded by the pig is 
also far greater in proportion to the food received, as 
plainly appears from the lower division of the table. The 
pig with its very large consumption of food has, in fact, 
to spend a smaller proportion of it on heat and work, and 
has thus a large surplus left to store up as increase. Of 
100 lbs. digested organic matter, the fattening ox spends 
about 77 for heat and work, the sheep 74, and the pig 57. 
The upper division of the table shows, however, that in a 
given time a pig does convert a much larger amount of 
food into heat and work than either sheep or ox ; this 
greater consumption probably represents internal work 
performed in the laying on of increase. The pig, with 
its rapid feeding, and high rate of increase, is undoubtedly 
the most economical meat-making machine at the farmer's 
disposal. 

The results given by sheep are seen to lie in nearly 
every case between those given by oxen and pigs, being 
however much nearer to the former than to the latter. 



102 THE CHEMISTRY OF THE FARM. 

The German experiments place the sheep below the ox as 
an economic producer of increase, instead of above it, as 
in the Eothamsted statistics just quoted ; the difference 
is probably due to the different breeds of animals experi- 
mented with. The inHuence both of breed, and of the 
individual character of the animal on the rate of increase 
whilst fattening is very considerable. 

The results relating to manure will be discussed in the 
next chapter. 

We have hitherto looked at the fattening period as a 
whole ; the rates of consumption and of increase are, 
however, very different in different stages of this period. 

As a fattening animal increases in size the quantity of 
food it consumes also somewhat increases, the require- 
ments of the body for heat and renovation of. tissue 
becoming greater as its weight and size are increased ; the 
stomach at the same time becomes larger. When the 
animal becomes very fat, the consumption of food falls 
off again, the rate of increase at this point being much 
diminished. 

As fattening advances the daily increase in live weight 
becomes gradually smaller, and the same amount of food 
will produce a steadily diminishing amount of increase. 
This IS partly because the increase during the later stages 
of fattening is drier, and contains a larger proportion of 
fat than in the earlier stages of the process. Partly also 
because the consumption of food for heat and work is 
increased with the increasing size of the body. More 
internal work must also be performed to add increase to a 
large animal than to a small one. These changes in the 
rates of consumption and increase are seen more strikingly 
in the case of pigs than with other animals, from the 
greater rapidity of the fattening process. The following 
table shows the average results obtained on sixteen pigs 
fattened at Eothamsted at the same time, the food being 
7 lbs. of pea meal per head per week, with an unlimited 



EELATIOiq^ OF FOOD TO AKIMAL REQUIREMEi^TS. 103 



supply of barley meal. The pigs had an average weight 
of lo5.8 lbs. when put up to fatten : at the end of ten 
weeks their average weight had become 276.3 lbs. 

FATTENING PIGS— WEEKLY CONSUMPTION OF FOOD AND 
RATE OF INCREASE. 





Food consumed. 


Increase in live 
weight. 


Food 
pro- 
ducing 
100 lbs. 
of in- 
crease. 


Per 
Bead. 


I^r 
100 lbs. 

live 
weight. 


Per 
Head. 


Per 

100 lbs. 

live 
ueight. 


First Fortni2:ht 

Second Fortuight.. 
Third Fortnight.... 
Fourth Fortnight.. 
Fifth Fortnight.... 

Whole Period 


- lbs. 
60.1 
67.5 
66.4 
66.0 
69.6 


lbs. 
39.7 
36.7 
30.9 
27.4 
26.3 


lbs. 
15.5 
17.4 
13.2 
12.9 
11.3 


lbs. 

10.3 
9.4 
6.2 
5.4 
4.2 


lbs. 
3S6 
388 
502 
511 
618 


65.9 


32.0 


14.1 


6.8 


469 



The figures in this table will explain themselves with- 
out further comment. The weights of food refer to meal 
in its natural state, and do not represent dry substance. 
The irregularities in the progression of the figures are due 
to the variable appetite and condition of the animals. 
Animals when first confined, and supplied with fattening 
food, always increase largely in weight during the first 
few weeks, after which the rate of increase diminishes to 
a considerable extent. 

The composition of the animal increase accumulated 
during fattening has been already given on page 65. 
The proportion of nitrogenous matter in this increase is 
very small, scarcely more than 7 per cent. For the 
purpose of fattening we must not, however, provide food 
containing as low a proportion of albuminoids as is stored 
up in the increase ; the animal body, in fact, requires a 
constant supply of albuminoids for the renovation as well 
as for the production of tissue. A diet tolerably rich in 



104 THE CHEMISTRY OF THE FARM. 

albuminoids is also both more digestible, and of greater 
feeding value, than a diet poor in this constituent. 

Wolff recommends a more nitrogenous diet for fatten- 
ing sheep than for oxen or pigs. The albuminoid ratio he 
recommends for fattening sheep is 1 : 4 — 5. For pigs, 
1 : 4 — 5 below 6 months, and 1 : 5 — 6 above that age. For 
oxen, 1 : 7 at the commencement of fattening, to be 
reduced to 1 : 5. 5 when fattening in earnest has set in, 
In all these diets, however, the amides have been reckoned 
as albuminoids, the error thus occasioned falling chiefly 
on the diets of the sheep and oxen. If we draw our con- 
clusions from the composition of diets of acknowledged 
good quality, and regard solely the true albuminoids 
present, we shall find that a diet having an albuminoid 
ratio of 1 : 9 — 10 is very suitable for fattening oxen ; a 
diet of 1 : 8 — 9 will give good results with sheej^, and one 
of 1 : 7 with pigs. Diets more nitrogenous may, however, 
be employed with more or less advantagCo 

Production of Wool. — Wool, besides the moisture and 
dirt which it naturally contains, is made up of three 
ingredients — suint, fat, and pure wool-hair. The suint 
is an excretion of the perspiration glands of the skin ; it 
chiefly consists of a compound of potassium with an 
organic acid containing nitrogen, of which little is known. 
Suint is soluble in water, and is in great part removed 
when the sheep are washed before shearing. In the case 
of Merino sheep the suint may amount to more than one- 
half the weight of the unwashed fleece ; but in the case 
of ordinary sheep, freely exposed to the weather, the quan- 
tity may be 15 per cent., or less. In a washed fleece the* 
fat may vary from more than 30 per cent, to 8 per cent., 
or less. Short fine wool contains the largest proportion 
of fat. Pure wool-hair contains about 16 per cent, of 
nitrogen. The quantity of nitrogen and ash constituents 
in unwashed wool has been already given on page 64. 



RELATION OF FOOD TO AKIMAL REQUIREME]5q"TS. 105 

The production of wool-liair and of wool- fat is practi- 
cally no greater when sheep receive a liberal fattening 
diet, than when the diet only suffices to maintain the 
ordinary condition of the animal; indeed, under poor 
treatment, the carcass may lose weight to some extent 
without the production of wool being seriously altered. 
With starvation, however, the yield of wool is considerably 
diminished. If sheep are kept on a poor diet for the 
mere production of wool, the amount of albuminoids sup- 
plied must not fall too low, wool-hair being formed entirely 
from this part of the food. 

Production of Milk.— The quantity of milk produced 
is largely determined by the individual character of the 
animal, and on the length of time which has elapsed since 
birth ; the quality of the milk is also affected, though to 
a less extent, by the same conditions. Subject to these 
natural limitations, both quantity and quality are greatly 
influenced by the character of the food supplied. 

A liberal diet is essential for a full supply of milk. 
Grreen fodder is favorable to a large produce, so also are 
brewers' grains. The diet of a milking cow should vary 
with the yield of milk, the object being to obtain as large 
a yield as can be reached without fattening the animal. 

The quality of the milk is considerably influenced by 
the richness of the diet. A diet of watery grass will prob- 
ably yield a moderate quantity of pure milk, the addition 
of oil-cake will increase both the yield of milk and also its 
richness. The alteration in the composition of milk by 
poor or liberal feeding is chiefly an alteration in the per- 
centage of solid matter ; the relative proportions of casein, 
butter, and sugar, are scarcely affected by the character of 
the diet. 

The quality of the butter is more or less influenced by 
the character of the food, some foods producing a hard, 
and others a soft butter. Rape-cake, oats, and wheat 



106 THE CHEMISTKY OF THE FARM. 

bran are reckoned in Denmark as first-class butter foods ; 
palm-nut cake and barley as second-class foods ; while 
linseed cake, peas, and rye are placed in the third class. 
The first-class foods produce a soft butter, the third-class 
foods a hard butter. By the employment of first and 
second-class foods with straw chaff, hay, and roots, an 
abundance of excellent butter may be produced through- 
out the winter. Turnips strongly flavor both milk and 
butter ; mangels are a better food for milk cows. 

As milk is a product far more nitrogenous than the 
increase of carcass obtained when an animal is fattened, 
cows in full milk will require a tolerably nitrogenous diet. 
Such a diet is naturally provided when cows feed on young 
grass and clover ; when hay, straw, and roots form the 
bulk of the food, it is imperative that cake or grain be also 
employed if abundance of milk is desired. Wolff gives 
1 : 5 as the albuminoid ratio most suitable for the diet of 
cows in full milk : deducting amides, the ratio will prob- 
ably be about 1 : 6 — 7. 



CHAPTER IX. 

RELATION OF FOOD TO MANURE. 

The quantity of manure produced by oxen, sheep, and pigs, under given 
diets— Proportion of the ash constituents and nitrogen of the food 
which appears in the liquid and solid excrements — Composition of 
the excrements of sheep and oxen — The relative manure value of 
various cattle foods — The value of the ash constituents and nitrogen 
of animal manure as compared with the same materials in artificial 
manures. 

The quantity of dry manure produced for a given 
quantity of food consumed lias been already mentioned. 
The figures in the table on p. 100 show that, with the diets 
assumed, the sheep produces for the same weight of dry 
food nearly twice as much manure as the pig, while the 
ox produces even more manure than the sheep. This dif- 
ference is due to the less digestible character of the food 
supplied to the sheep and ox. The quantity of manure 
produced during the same time, and for the same body 
weight, is however very similar with the three animals, 
the greater consumption of food by the pig counter- 
balancing its lower rate of manure production. 

The only constituents of food which are of importance 
as ingredients of manure are the nitrogenous substances, 
and the ash constituents. If the live weight of an animal 
remains unchanged, and there is no production of milk, 
the quantity of nitrogen and ash constituents voided m 
the manure will be the same as that contained in the food 
consumed ; the albuminoids and ash constituents of the 
food used for the renovation of tissue being in this case 
equivalent to the quantity yielded by the degradation of 
tissue. In cases where the body weight is increasing, or 
milk is being produced, the amount of nitrogen and ash 
constituents in the manure will be less than that in the 
107 



108 THE CHEMISTRY OF THE FARM. 

food in direct proportion to the quantity of these sub- 
stances which has been converted into animal produce. 

A part of the albuminoids and ash constituents is left 
undigested during the passage of the food through the 
alimentary canal ; these are voided in the solid excrement. 
The digested nitrogenous matter and ash constituents 
pass into the blood, a part of them may be converted into 
animal increase if the animal is gaining in weight or pro- 
ducing milk, and the remainder is finally separated from 
the blood by the kidneys, and is Yoided in the form of 
urine. The albuminoids and amides are oxidized into urea 
before being expelled from the system. In the case of 
herbivorous animals hippuric acid is also formed in vari- 
able quantities, and is found as an ingredient of the 
urme. 

The proportion of the nitrogen in the food which will 
appear m the solid excrement is determined by the diges- 
tion coefficient of the albuminoids. Thus 79 has been 
ah'eady given as the digestion coefficient of the albumi- 
noids of barley meal when consumed by a pig ; it follows 
that m this case for 100 of albuminoids consumed 21 will 
b.e voided in the solid excrement, and 79 pass into the 
blood. It has been already stated that 500 lbs. of barley 
meal, containing about 53 lbs. of albuminoids, will in the 
case of the pig produce 100 lbs. of animal increase, con- 
taining 7.8 lbs. of albuminoids. It follows from these 
data that for 100 lbs. of albuminoids consumed, 14.7 are 
stored up as carcass, 21 appear in the solid excrement, 
and 64.3 as urea, etc., in the urine. In the same way, 
by deducting the ash constituents stored up from those 
present in the food, we can arrive at tSe quantity of ash 
constituents voided in the manure. Calculatina: in this 
manner the relation of food to manure in the case of the 
fattening ox, sheep, and pig, receiving the diets assumed 
in previous calculations (p. 100), we arrive at the follow- 
ing conclusions : — 



KELATI02!^^ OF FOOD TO MAKUEE. 109 

NITROGEN STORED UP AND VOIDED FOR 100 CONSUMED. 





Stored 

upas 

increase. 


Voided 

as solid 

excrement.'^ 


Voided 
as liquid 
excrement. 


In t tal 

excrement. 


Oxen 


3.9 
4.3 

14.7 


22.6 
16.7 
31.0 


"73.5 
79.0 
64.3 


96.1 
95.7 
85.3 


Sheep 


Pms 





ASH CONSTITUENTS STORED UP AND VOIDED FOR 
100 CONSUMED. 



Oxen . 

Sheep . 
Pigs.. 



Stored up 
Increase. 



2.3 
3.8 
4.5 



Voided in total 
excrements. 



97.7 
96.2 
95.5 



The proportion of the nitrogen and ash constituents of 
the food which is stored up in the body of a fattening 
animal is in all cases very small. In the case of each 
animal mentioned in the above tables more than 95 per 
cent, of the ash constituents of the food find their way 
into the manure. With oxen and sheep more than 95 
per cent, of the nitrogen of the food are likewise thus 
voided. The pig is seen to retain the largest proportion 
of the nitrogen of its food ; this is clearly owing to the 
greater proportion of increase which the pig produces for 
a given weight of food consumed. 

The amount of nitrogen voided in the urine is seen to 
be three or four times the quantity contained in the solid 
excrement. This relation will vary greatly according to 
the character of the diet. If the food is nitrogenous, and 
easily digested, the nitrogen in the urine will greatly pre- 
ponderate ; if, on the other hand, the food is one imper- 

* The quantities of nitrogen given in this column are a little below 
the truth, as besides the undigested albuminoids some nitrogenous bili- 
ary matter is present in the solid excrement. With oxen and sheep the 
amount of biliary matter in the excrement is very small ; with pigs it is 
more considerable. In the case of the pig the nitrogen in the solid ex- 
crement should probably stand as 25^, and that in the liquid as 59.3. 



110 



THE CHEMISTEY OF THE EAEM. 



fectly digested, tlie nitrogen in the solid excrement may 
form the larger quantity. When ordinary hay is the 
diet, the nitrogen in the solid excrement will generally 
somewhat exceed that contained in the urine ; with a 
straw diet the excess in the solid excrement will be much 
greater. On the other hand, grain and cake, and especi- 
ally roots^ yield a larger excess of nitrogen in the urine. 

The ash constituents are very differently distributed in 
the solid excrement and urine ; in the former, the lime, 
magnesia^ and phosphoric acid are chiefly found, while 
the latter contains nearly all the potash. With sheep fed 
on hay, about 95 per cent, of the lime contained in the 
food, 70 per cent, of the magnesia, and 83 per cent, of 
the phosphoric acid were found in the solid excrement, 
but only 3 per cent, of the potash. 

A fair idea of the general composition of the solid ex- 
crement and of the urine, is given by the following table. 
The sheep were fed on meadow hay ; the oxen on clover 
hay and oat straw, with about 8 lbs. of beans per day. 

PERCENTAGE COMPOSITION OF SOLID AND LIQUID EXCRE- 
MENT. SHEEP FED ON HAY. 





Solid excrement. 


UHne. 


Fresh. 


Dry. 


Fresh. 


Dry. 


■prater 


66.2 

30.3 

3.5 


89!6 
10.4 


85.7 
8.7 
5.6 


Olio 
39.0 


Ortrnnip l^nt.t.P.r 


Ash 




"NJif rrkirpn . 


0.7 


2.0 


L4 


9.6 




OXEN WITH NITROGENOUS DIET. 




Solid excrement. 


Urine. 


Fresh. 


Dry. 


Fresh. 


Dry. 


Water 


86.3 

12.3 

1.4 


89.'7 
10.3- 


94.1 
3.7 
2.2 


63!o 
3T.0 


Oi'O'aDic Matter 


Ash 




Nitrogen 


0.3 1.9 


1.2 20.6 



RELATIOJ^ OF FOOD TO MAJEURE. 



Ill 



Both the solid and liquid excrements of the sheep are 
far drier, and therefore more concentrated, than those 
of the ox, whose food includes a much larger quantity of 
water. 

The extreme richness of the urine, both in ash constit- 
uents and nitrogen, is very evident. In the case of the 
more highly-fed oxen, the dry matter of the urine is seen 
to contain over 20 per cent, of nitrogen. 

The relative value of the manure produced by different 
foods is determined by the relative richness of the foods 
in nitrogen and ash constituents, but chiefly by the amount 
of nitrogen, this being the most costly ingredient of pur- 
chased manure. The average amount of nitrogen, and of 
the two most important ash constituents contained in 
ordinary cattle foods, is shown in the following table : — 

MANURIAL CONSTITUENTS IN 1,000 PARTS OF ORDINARY 
FOODS. 



Cotton Cake (decorticated). . , 

Rape Cake 

Linseed Cake 

Cotton Cake (undecorticated), 

Linseed 

Palm-l<:ernel Meal (Engiish).. 

Beans 

Peas 

Malt Dust 

Bran 

Oats 

Wheat 

Barley 

Maize 

Clover Hay 

Meadow Hay 

Bean Straw 

Wheat Straw 

Barley Straw 

Oat Straw : 

Potatoes 

Manocels 

Swedes 

Carrots 

Turnips 



Dry. 

Matter. 



900 
900 
880 
885 
905 
930 
855 
857 
905 
865 
870 
856 
860 
886 
840 
857 
840 
857 
850 
830 
250 
115 
107 
143 
83 



Nitrogen. 



66.0 

48.0 

45.0 

39.0 

36.0 

25.0 

41.0 

86.0 

38.0 

22.0 

20.6 

18.8 

17.0 

16.6 

19.7 

15.5 

10.0 

4.8 

5.0 

5.0 

3.4 

1.9 

2.4 

1.6 

L8 



JFbtaah. 



15.01 

13.2 

14.7 

20.1 

12.3 

5.5 

12.0 

9.8 

19.5 

14.8 

4.5 

5.4 

4-. 9 

3.6 

19.5 

16 8 

25.9 

5.8 

9.7 

10.4 

5.6 

3.9 

2.0 

3.2 

2.9 



Phos- 
phoric 
Acid. 



31.2 

24.6 

19.6 

22.9 

15.4 

12.2 

11.6 

8.8 

17.2 

32.3 

6.2 

8.0 

7.3 

6.1 

5.6 

3.8 

4.1 

2.6 

2.0 

2.5 

1.8 

0.7 

0.6 

LO 

0.6 



112 THE CHEMISTRY OF THE FARM. 

The oil-cakes yield tlie richest manure, as they contain 
the largest amount of nitrogen and phosphoric acid, with 
a considerable amount of potash. Next to these come the 
leguminous seeds, malt-dust, and bran. Clover hay 
yields a richer manure than the cereal grains, while 
meadow hay stands below them. The cereal grains and 
the roots contain about the same proportion of nitrogen 
in their dry substance ; the roots, however, supply much 
more potash. Potatoes stand below roots in manurial 
value. Straw takes the lowest place as a manure-yielding 
food ; bean and pea straw are more valuable for this pur- 
pose than the straw of the cereals. 

The ash constituents present in animal manure have 
probably the full money value of the same constituents in 
artificial manures, but the nitrogen has on the whole a 
lower value than the nitrogen of ammonium salts or nitrate 
of sodium. The nitrogen of the urine is indeed quite as 
valuable as the nitrogen of ammonium salts. When ap- 
plied to the soil the nitrogen of urine is rapidly converted 
into nitrates, the form of nitrogen most suitable for plant 
nourishment. But, on the other hand, the nitrogen of the 
solid excrements is not in a form suitable for plant food, 
and will be very slowly converted into nitrates in the soil. 

Animal manure is probably more immediately available 
for the use of plants when applied directly to the land, 
than when previously mixed with a great bulk of litter. 
Fermentation with litter probably results in the formation 
of nitrogenous humus compounds, which are insoluble, 
and decompose but slowly in the soil. 

The feeding of animals on the land is a mode of apply- 
ing manure which has many advantages ; but its distri- 
bution is irregular, and in autumn or winter the manure 
is subject to loss by drainage. The most effective plan 
of application is as liquid manure to growing crcns. In 
winter time the use of litter, and the preparation of 
farm-yard manure (best under cover), becomes a necessity. 



CHAPTER X. 
THE DAIRY. 

The constituents of milk — The conditions affecting its richness — The fat 
globules — Modes of raising cream — Composition of cream — Compo- 
sition of skim-milk — Churning — Composition of butter— Butter-milk 
—Manufacture of cheese— Composition of cheese— Whey— Neces- 
sity for cleanliness. 

Milk. — The general composition of colostrum, and of 
ordinary cow's milk, has already been given on page 95, 

The albuminoids of milk embrace two constituents of 
similar composition, casein and albumin. Casein is coag- 
ulated by the addition of acids, or by rennet, but not by 
boiling. Albumin is not coagulated by rennet, or by 
most acids, but is coagulated by heat. In colostrum albu- 
min largely preponderates, so that the milk coagulates on 
boiling ; in ordinary cow's milk the albumin forms but 
one-ninth of the total albuminoids. 

The fat of milk chiefly consists of the glycerides of 
palmitic and oleic acid. The glycerides of stearic, myristic, 
lauric, capric, capryllic, caproic, and butyric acid are also 
present in small quantity. The last four of these acids 
are, when in the free state, more or less soluble in water. 
The glycerides of oleic acid and of the soluble fatty acids, 
are fluid fats at ordinary temperatures, the remaining fats 
are solid. The proportion of fluid and solid fats varies 
somewhat with the diet and condition of the animal ; 
in summer time the proportion of fluid fats is greater 
than in winter. 

The sugar contained in milk is known by chemists as 

lactose. When milk turns sour the lactose is converted 

into lactic acid ; this acidification of the milk induces the 

coagulation of the casein, and the milk curdles. The 

113 



114 THE CHEMISTRY OF THE FARM. 

ordinary souring of milk is the work of a ferment, Bac- 
terium lactis ; when this ferment is excluded no souring 
takes place. 

Cow's milk has generally a specific gravity between 
1.028 and 1.032. As the removal of cream raises the 
specific gravity, which can be brought back to the normal 
point by the addition of water, no safe conclusion as to 
the quality of milk can be based on this indication. 

The composition of cow's milk is affected by various 
circumstances ; under extreme conditions it may contain 
from 10 to 16 per cent, of dry matter. The milk is poorer 
when the quantity produced is large, or the diet insuffi- 
cient, and richer when these conditions are reversed. A 
cow is generally in full milk from the second to the 
seventh week after calving ; after this period the milk 
gradually diminishes in quantity, but increases in rich- 
ness. A separation of cream takes place in the udder ; 
the milk first drawn is poor in fat, and the richness 
increases as milking proceeds, the last drawn milk con- 
taining two or three times as much fat as the first drawn. 
Tlie milk of old cows is said to be poorer than the milk 
of young cows. 

The relation of food to the production of milk and 
butter has already been considered on page 105. 

Cream. — The fat of milk occurs in the form of globules ; 
the largest are about .0005 to .0006 inch in diameter, the 
smallest may be one-tenth this diameter, or even less. 
The average size of the globules is different with different 
breeds of cattle. The size appears to diminish as the 
time from calving increases. The fat globules are m most 
cases coated with a thm albuminous covering. As the 
fat globules have a lower specific gravity than the serum 
m which they float, thoy tend to rise to the surface, 
where they form a layer of cream. The largest globules 
are the first to rise, the smallest never rise at all, being 



THE DAIRY. 115 

too heavily weighted by tlieir albuminous covering. Milk 
containing an abundance of large globules is best for but- 
ter-making, as the cream then quickly and perfectly rises ; 
but milk with small globules is probably best for cheese- 
making, as a more even distribution of fat throughout 
the curd is then obtained. 

Milk, when it leaves the cow, will have a temperatirre 
of about 90° Fahr. ; when set for cream it should be 
cooled as quickly as possible, as changes in composition 
would rapidly occur at a high temperature. Milk is 
usually set for cream in shallow vessels, the depth of milk 
being perhaps 3 inches ; in these vessels the milk stands 
for thirty-six to forty-eight hours, until the cream has sep- 
arated. • Under these conditions a large surface is exposed 
to the influence of air, and a maximum amount of change 
takes place ; the result is a decomposition of a part of the 
albuminoids and fats, the production of lactic acid, and 
the partial curdling of the milk. The cream obtained in 
this way is contaminated with curd, and contains various 
strongly flavored products of decomposition, which de- 
teriorate the quality of the butter. 

On Swartz's plan the milk is placed in metal pails, 16 
inches deep, and surrounded by ice. The cream rises 
quickly, and can all be obtained in twelve to twenty-four 
hours from the time of setting. Cream thus prepared is 
perfectly sweet, and free from curd, the low temperature 
at which the milk has been kept having reduced chemical 
change to a minimum. It occasionally happens that milk 
will not yield its cream at low temperatures ; this is 
sometimes the case with the milk of cows several 
months after calving, and especially when receiving a 
winter diet. 

A third plan of separating cream is by subjecting the 
milk to extremely rapid horizontal revolutions in a centri- 
fugal machine ; under these circumstances the fat globules 
rise into the center of the revolving mass. In Laval's 



116 THE CHEMISTRY OF THE FARM. 

macliiue the new milk enters in a continuous stream, and 
is immediately separated into cream and skim-milk, the 
former leaving the apparatus by a pipe at the tojD, the 
latter by another pipe from the side. The cream thus 
obtained is, of course, perfectly sweet. 

Cream varies considerably in composition. Good cream, 
not scalded on the Devonshire plan, may contain 55 to 65 
per cent, of water, and 25 to 40 per cent, of fat. Casein 
and the other constituents of milk are present in small 
quantity. In sweet cream the casein may be about one- 
tenth of the fat ; in cream which has soured during set- 
ting the casein forms a much larger proportion. 

Skim-Milk. — Milk thoroughly skimmed in the ordinary 
way will contain about 0. 8 per cent, of fat ; more than 
this quantity is frequently present. When ice has been 
used, the percentage of fat left in the milk will be 0. 3 to 
0.6 ; and when the centrifugal machine has been employed, 
0.2 to 0.5. The two latter processes are thus the most 
effective for the removal of cream. Ordinary skim-milk 
will contain about as follows : — Water, 90.0 ; albuminoids, 
3.7; fat, 0.8; sugar, 4.8; ash, 0.7. Its specific gi'avity 
is generally 1.034 to 1.037. Skim-milk is a very nitro- 
genous food, the albuminoid ratio being as high as 1 : 1.7. 

Butter. — The object of butter-making is to bring about 
the union of the fat globules which in milk and cream 
have existed separate from each other. The skilled butter- 
maker is hot, however, satisfied with producing a solid 
mass of butter-fat ; for butter to be of good quality it 
must possess a certain texture and gram, and be neither 
hard nor greasy ; this desired result can only be attained 
by churning at a favorable temperature. If the tem- 
perature of the cream is too low, the butter will be long 
in coming, and will be hard m texture. If the tempera- 
ture is too high the butter will come very speedily, but 



THE DAIRY. 117 

the product will be greasy, destitute of grain, and deficient 
in quantity. Ko temperature can be fixed as the best at 
which churning should always take place. The propor- 
tion of solid and fluid fats in the milk yaries somewhat 
with the diet of the cows, and this necessitates a change 
in the temperature. A rather higher temperature will be 
required in winter than summer ; the temperature must 
also be higher for sour cream than for sweet cream. 
Generally speaking, perfectly sweet cream should be 
l^laced in the churn at 50° to 55° Fahr., and sour cream 
at 52° to 60°. 'When sour milk is churned for butter the 
temperature must be about 65°. The exact temperature 
most suitable for churning may be ascertained by record- 
ing every day the temperature employed, with the length 
of time occupied in churning, and the amount and char- 
acter of the produce ; when this is done the temperature 
for each day can be regulated from the experience of the 
preceding working. The temperature will rise several 
degrees during churning. 

Churning must always be stopped as soon as the butter 
comes, any over-churning spoils the texture of the butter. 
The butter is then separated from the buttermilk, washed 
with cold water, and after standing to solidify is carefully 
worked and pressed to expel all watery matter ; over- 
working in this stage will also spoil the grain, and make 
the butter greasy. Butter made from perfectly sweet 
cream keeps far better than butter made from sour cream, 
as the latter always contains curd, a substance very prone 
to change. Salt is generally added to improve the keeping 
quality of butter. 

First-class butter will contain about 10 per cent, of 
water, and not more than 0.5 per cent, of casein, but in 
ordinary butter these proportions are greatly exceeded. 
Of the fatty acids in butter about 6 per cent, are soluble 
in water when separated from the glycerol with which 
they are combined ; this fact serves to distinguish butter 



118 THE CHEMISTRY OF THE FARM. 

from other animal fats in which soluble fatty acids are 
absent. When butter becomes rancid the glycerides of 
the fatty acids are partly decomposed, and the fatty acids 
liberated ; the odor and flavor of rancid butter are largely 
due to free butyric acid. 

Buttermilk. — The liquid remaining in the churn after 
the separation of the butter from the cream has been but 
little investigated ; it must vary a good deal in composi- 
tion. Danish experimenters found that when churning 
the cream from 100 lbs. of new milk .07 to .20 lb. of fat 
was left in the buttermilk. 

Cheese. — This substance is prepared by the action of 
rennet on milk. The rennet solidifies the milk by 
separating the casein from solution ; the fat globules are 
separated at the same time, being entangled in the curd 
formed. Eennet is a watery extract prepared from the 
fourth stomach of the calf ; its power of coagulating 
milk is apparently due to the presence of a ferment, 
which doubtless plays a similar part in the ordinary pro- 
cess of digestion in the calf's stomach. The action of 
rennet is very slow in the case of cold milk, it becomes 
much more energetic as the temperature rises ; at 135"^ 
Fahr. it ceases to act. Milk becomes sour when curdled 
by rennet, but the production of acid (lactic acid) is not 
essential to the curdling. 

The composition of cheese depends principally on that 
of the milk from which it is made ; rich cheese is made 
from new milk, cream being sometimes added to the milk 
for the production of the richest sorts ; poorer kinds of 
cheese are made from milk wholly or partially skimmed. 

The temperature at which the milk is curdled is of 
great importance. If the temperature is low, the curd 
is very tender and the whey difficult to separate ; if, on 
the other hand, the heat is too great, the curd shrinks too 



THE DAIRY. 119 

much, and becomes hard and dry. A temperature from 
74° to 84° is generally employed, the lower temperature 
for thin cheeses, the higher (80° to 84°) for thick. 

When the curd is sufficiently firm it is carefully cut in 
all directions, and the whey allowed to drain off. To 
facilitate the drainage of the whey the curd is often 
heated after cutting, with the view of making it shrink 
and harden ; the temperature used at this point must not 
exceed 100° Fahr. The drained and broken curd is next 
put into a press, to remove more effectually the last 
portions of whey. It is then pulverized in a mill, salted, 
again passing through the mill, and is then ready for 
filling into the frames. Curd when put into the frames 
should contain, according to Voelcker, about 54 per cent, 
of water when thin cheese is to be made, and not more 
than 45 per cent, if thick cheese is manufactured. The 
curd from skim-milk will contain much more water than 
a curd rich in butter. The frames filled with curd are sub- 
jected to a gradually increasing pressure for several days. 
The cheese is then removed from the frame and placed 
in the cheese-room to ripen. 

Cheese ripens best at a moderately warm temperature ; 
about 70° is a suitable degree of heat. During the opera- 
tion a loss of water takes place, the loss being greatest in 
the case of poor cheese. If decay, or a growth of mould 
occurs, a further considerable loss of weight takes place, 
the casein and fat of the cheese being decomposed by 
the organic life thus introduced, while carbonic acid, 
ammonia, and a variety of other products are formed. It 
was once believed that fat was produced during the 
ripening of cheese ; this however is not the case. 

A very rich cheese, as old Stilton, may contain about 
20 per cent, of water, 44 per cent, of fat, and about 29 
per cent, of casein. In a good Cheddar or Cheshire cheese 
we should find about 33 per cent, of water, 33 per cent, 
of fat, 28 per cent, of casein, and about 3 to 4 per cent. 



120 THE CHEMISTRY OF THE FAEM. 

of ash constituents, nearly half of which would be com- 
mon salt. In skim-milk cheeses the percentage of water 
is greater, and that of fat less. Thus a poor single 
Gloucester may contain 38 per cent, of water, 22 per 
cent, of fat, and 31 per cent, of casein. In skim-milk 
cheese made in Denmark, from milk from which the 
cream has been yery completely removed by the ice sys- 
tem, only 4 to 5 per cent, of fat are present. 

\fiicy, — The whey which drains from the curd in 
cheese-making is a perfectly transparent liquid, contain- 
ing the sugar and albumin originally present in the milk ; 
it should not contain more than a trace of butter. If, 
however, the curd has been roughly treated, the milk has 
been rich, and the temperature high, larger quantities of 
butter will be present, and the cheese suffer in conse- 
quence. When whey is rich in butter it is generally 
allowed to stand until the butter has risen ; the butter may 
then be added to the next churning. The average com- 
position of whey is shown by Voelcker's analyses to be as 
follows : — Water, 93.0 ; albuminoids, 1.0 ; fat, 0.3 ; sugar 
and lactic acid, 5.0; ash, 0.7. The albuminoid ratio is 
1 : 5.2. 

In all the operations of the dairy the greatest cleanli- 
ness must be observed ; all vessels should be washed with 
hot water as soon as done with, to destroy any adhering 
ferment. Without such precautions no good butter or 
cheese can be made. 



